How does a SO feel different from a very good friend?

A good friend (platonic relationship) is someone I can see every day, talk to about anything, and I want them in my life regularly. I personally cannot spend 100% all my time with someone who is just a good friend.
A romantic relationship is a good friend who I can live with and want to share a blanket and cuddle with at the end of the day. It's someone I might want to hold hands with, kiss, or sleep with. It's someone I want to come home to at the end of a good day to share good news, or end of a bad day to make it better.
A sexual relationship is someone I want to kiss and have sex with.
There are overlap. Romantic friends and friends with benefits are pretty common terms. Having a romantic relationship with sexual interest often ends up in bad relationships; I've heard this described as "feels like it should work" or "I loved them but I didn't like them."
- And ideally, when you find someone that is in all three circles for longer than a honeymoon (or refractory) period, that's the one you marry!
  
  Very true! Although honeymoon phase/stage can last quite a while, individuals depending.

I think this is all personal preferences, but by default many times with an SO you usually are both building towards a common goal together to cement your future together. Again, I’m sure that’s not the case for everyone but I am just speaking generally.
With a “very good friend” that might not necessarily be the case - but these lines can all get very fuzzy depending on people’s outlooks, perspectives, wants etc.
I probably haven’t given you much clarity here but I also think many people have wrestled with at one point or another in the dating world.
- For me: SO (and if they’re not the same: spouse) is more about becoming a team.
  With a really good friend, unless you have something very special, you’ll probably not tether your lives together and commit to going through the rest of your days together.
  There’s something that happens over time when you have that commitment that really bonds you (so I’ve found). I haven’t felt it with a friend, and the closest I’ve come to it otherwise is with family (though there’s even less commitment between family members, I’ve found).
  It’s hard, but it’s also great.

An SO will align their goals with you. A best friend may find another goal in life and go off on their own. A friend isn't tied to you, and you'd support them if they 'leave' you to seek their own fortune. A partner stays with you and you and they need to find ways to reach your goals together. There's a stability and security to a partner that you don't get, no matter how close your friend is.

This is an interesting question. My husband is my ONE. Wherever he is, that's home. We are absolutely best friends & more. We share absolutely everything & neither of us ever have to worry about the other one waking up one day & deciding to move on without the other.
I realize I'm lucky. Not every relationship is anywhere close to that. I was married before & lived with others... And I thought the "one true love" stuff & long-term monogamy was complete BS until he & I got together.
But not everyone wants the kind of relationship we have & that's fine too. I have plenty of independent & awesome friends who have great friends, great lives, great hobbies; they adventure, travel, are fulfilled, etc etc all without an SO. Others who are in great relationships but are much more prone to doing things separately, and that's what works for them.
So maybe if you don't have that drive to find that relationship, maybe it's not for you or maybe you just haven't met the right kind of person yet. Your SO relationship can ultimately be whatever you want it to be, provided you find a partner agreeable with it. Best wishes either way!

My wife says she got to marry her best friend, and I say that I get to bang my best friend whenever we want.

In my eyes that distingueshes a "normal" friendship and a life partner is the planning for the future and being a team. You make big life decisions (moving house, career changes, medical decisions) together thinking of the best outcomes for both as a team. You could be a life partner with a non romantic totally platonic friend, but that's usually not the case you see represented.
- Many romantic relationships evolve more or less into this over time also.

You’re overthinking it. It starts as good friends and grows from there. You don’t have to know how it works right now. Just find someone who you work well with and go from there.

You get a teammate for your battles against the world, and benefits.

Yeah, I'd say SO generally are like great friends (with benefits), but often, over time you end up doing so much stuff with them that they eclipse any other individual friend. And eventually (especially if you end up living together) they become such a part of your day to day life they can begin to feel like an extension of yourself (or rather, that you're both part of one being) and it's hard to live with out them. I remember laughing at my dad for wanting to phone my mum everyday when he was away on business. I'd be like "what do you even have to talk about? You see each other all the time" But now, if I had a day where I didn't at least message with my partner I'd feel so isolated.

I'm wondering if you might find these a helpful starting point:
https://breezewiki.com/lgbtqia/wiki/Aromantic
https://en.wikipedia.org/wiki/Queerplatonicrelationship
(or not, sorry if I'm misunderstanding and just confusing you further)
- Well, I guess it feels more like, all I have to offer is friendship with intimacy. But not that I don't want to. What I mean to say is: Is not being (or not knowing how to be) a romantic type the same a someone who is aromantic?
  
  You might be aromantic, or it might just be that you haven't met a person or had the time with a person to develop romantic feelings.
  
  I don't think I can answer that for you unfortunately, it's something for you to investigate with yourself, and at some point possibly with a potential partner too. There are also aro/ace communities around (sadly the ones on the fediverse seem pretty dead) where you can talk your feelings through with people who are going through a similar experience.
  Either way, having friendship and intimacy to offer is a lot, and enough, don't let any social constructs make you feel otherwise.
  At the end of the day "relationship" is a pretty wide concept and it includes friendships as well as sexual and other partnerships, and no two are alike (despite what we've generally been socialised to believe - either completely platonic or the hetero-romantic boy meets girl, they date, fall in love, move in together, get married, have kids). What's important is that you find relationships that work for you (and the other person/people involved of course), and the only way to make sure of that is to communicate as openly and honestly as you can with yourself and each other (so for example what you define as a "friendship with intimacy" might qualify as a romantic relationship to some but not to others).
  Also - aromanticism, like other orientations, is a spectrum, so you might be greyromantic or demiromantic, which probably only confuses things more (I know it did for me, and so I've never really taken the time to figure out exactly where I fit on the aro/ace spectrums beyond knowing I'm on them), but just know that there are options for you to "try on" and see which fits most comfortably (if any!).

Intimacy, whether its shared via sex with a partner or deep connection via friendship, manifests much stronger and more complex emotions.
Things you wouldnt care about become more important. Do i have this persons trust, do they love me back, why do they do that one thing with their teeth?!

My wife is different than my friends because we literally live together. All decisions are made with the both of us in mind. As a result, we know each other better than just about anyone else, and that level of emotional intimacy is tough to find anywhere else. Don’t get me wrong, I have a few very good friends as well, but I don’t talk about the same things with them as I do my wife.
Having an honest to God companion to share the ups and downs in life is amazing. The ups are sublime, the downs help us both be more introspective and end up bettering ourselves.

It's very exclusive and more intimate physically and emotionally than a good friend. That's my interpretation anyway.
besides you know what). And should it be?
We're adults here. You can say the word sex on the internet, and yes.
To me, it seems like you may not be the type of person that feels like they need intimacy. If you want it, however, then that should be ok too. That is a major difference (for many) in people who are in relationships, and people who are just good friends. It's not the sole defining characteristic, no, but a big one none-the-less.
...they just want a one particular friend with benefits
Why can't it be both though? I think there's nothing wrong with that, in my mind. I suppose a big consideration would be if you live together or not, or want to/plan to.
Another thing to consider is that SO relationships are typically seen as more static/permanent while good friends are considered more dynamic/fleeting.
In my experience, relationships (all relationships) are more dynamic than static. Realities of our mortality.
- We're adults here.
  You sure about that?
  
  Well, maybe not.
  #¯(ツ)_/¯

Well basically love is a form of psychosis where someone becomes the most important thing to you and your whole reality bends around that. You feel a deep abiding satisfaction and comfort just being in their presence or hearing their voice. Your personal identity becomes secondary to your shared identity as a couple and your connection to them is a core part of your emotional state and thought process. Anything that contradicts being with or caring for them is basically impossible to even think. This can be really wonderful or really horrible depending on the circumstances.
- This sounds more like infatuation than love, TBH.
  
  The way I see it infatuation is just the surface feeling, love is when it becomes a more permanent core motivation and foundation of what you do and think. What do you think the difference is?

This is an interesting question. In my opinion, romance, true romance, is built over time through consistent effort. Nobody truly loves someone the moment they see that person. Anyone who thinks that they fell in love at first sight, well, I call that puppy love. It's the kind of "love" that middle school children engage in.
I think that distinction doesn't get emphasized enough. And all the romance movies that glorify "passionate love" aren't helping. If you were to ask me, true love is what's left after the passion has died out. I know some people describe it as being like a best friend. I won't necessarily say that it's wrong, since it's a pretty close approximation. But I don't think that's the full picture.
Have you ever lived with a roommate? A lot of it is about balancing each person's wants and compromising. A lot of it is about forming a strong system of habits that won't anger the other person. Who does the dishes? Who takes out the trash? Who keeps track of groceries? What do you do if the other person is upset? Even down to simple things, like what to do if you and the other person can't agree on what to eat. If you had a roommate at any point in your life, you'd probably understand what I mean. Having an SO is essentially like that, but much harder, because you're sharing many more things than with just a roommate. In my opinion, true love is about aiming to set up that equilibrium where both people enjoy living with the other person.
To summarize, if you were given a choice between living with your SO or living alone, and you end up preferring to live with your SO, then I would consider that true love.
- In my opinion, true romance has Christian Slater and Patricia Arquette.

I don't try to fuck my friends hah. I can sit for hours with my SO and not utter a word and just do my shit. I don't have to be on and allowed to be irritable.

Opinions vary, but it's my opinion out of all the things two people need to be compatible, friendship is by far the most important. At best sex only lasts, what eight to ten hours, the rest of the time you need a friend. When you are younger, you may be doing it all over the house but when you're older things typically slow down or there may be times when someone is injured, tired, stuck at work, whatever. In those times understanding, compassion, commiseration and cooperation are important. If your partner is your best friend, you're never lonely and you can share things. It's so much harder when you have very little in common with your partner.
Guess I'm rambling now, but this is how I see it.
Good luck to you.
- Sex only lasts 8 to 10 hours? Are you a fucking Viagra spokesperson?
  
  OK, perhaps I was exaggerating a bit. Perhaps it's more like 10 to 12, but the point still remains that you have to occupy the rest of that time and it's best if you have a good friend to do that with.
  
  He said "At best".
  It's not so unreasonable if you have an open interpretation of what counts as sex. Certainly PiV penetration won't last that long by itself. But if you count foreplay, the afterglow, and subsequent sessions all as one, it becomes reasonable, especially in your 20s.

Your end goal is falling in love
You’ll know when that happens
- First goal is finding friends. This sounds like a joke but I'm serious don't force a relationship. Meet people, get friends. If you align, you align. If not, you've made a friend. If not, you've learned what you don't like or learned what others don't like.
  Make friends. Make a best friend. Then if a relationship blooms, at least it wasn't forced. You met and found out what you liked before hand.
  
  Yeah. But it happened me a couple of times that I fell in love at first sight before even getting to know the person. Then I loved the person too. Maybe it won’t last. But sometimes it’s just pure chemistry in our brain. Never force a relationship of course. And love can blossom with time. But if you stay with a person and it just feels like a close friend, you are probably not in love. And should move on.

I'm not sure about you, but the best partner I could ever think of is one that is also your best friend; they are easy to talk to, comfortable to be with, you can joke with them, appreciate the world with them, and generally see them as your best friend, with the layer of also feeling profound physical, emotional, and (possibly) sexual intimacy. You genuinely love each other in the most pure sense of the word and can depend on each other more certainly than anyone else, because you can share anything with them, because they are your closest friend in the world.
However, most of it depends on what you want. Simply think about what you want most in a partner, and then look for that. Are you looking for someone who is also figuring out what to do in their love life? Do you need someone to push you in a direction? You have far more agency in your choices than you think you do.
Perhaps first, you should meditate on what you are looking for before you begin seeking it.

It's when there's so much love, the SO becomes family.
- Homies are family too, third cousins get outta here

You can bone them regularly without making things awkward
- Clearly you're only friends with boring people

To me, the key difference is just how much you can be yourself around that person, without any feeling of self consciousness or shame. Even with very good friends, there are still things about yourself (physical or otherwise) that you don't let them see.
Also, my wife IS my best friend.

I feel like a good SO is just a best friend with benefits. Someone you can do all the same stuff as a bestie with, and feel the same way around, but you also are sexually attracted and fuck.

I don't think of relationship types as distinct categories. I view relationships as a many-dimensional spectrum. All relationships fall somewhere on this spectrum. Some are sexual, some have romance, some have shared hobbies, some have admiration etc.

allow me to sum up interpersonal relationships between all 8 billion people in one sentence:
you can't
but, in a nutshell... physical attraction is usually important, so is romance... usually a commitment to this person in terms of time and future plans where they become more like family (and maybe eventually actually family if you have kids)
there's such a crazy spectrum of the ways in which people could get along and consider themselves "in a relationship".
every rule or tendency is constantly broken, it escapes definition.
in general, it begins with attraction and flirting, or it's cemented as a friendship...
and, poetically, i'd say it's a relationship when they start to see themselves as an entity, and of course others will see them like that too... a sort of hive-mind develops...
sorta like when celebrity couples get a combo nickname....

If you’re wondering this, you might be aromantic. I’m not saying you are, it just strikes me as similar to a conversation I’ve had with an aro/ace friend.
If you already know, please ignore me, but if not, maybe check it out and see if hearing about aromantic experiences can help.

Obviously relationships are messy and complicated and varied, but generally the big difference is a commitment to a future together. For example, committed partners might pool finances, or have a kid together - the sort of things that you plan on working together on the rest of your life.

I feel the same way. I still don't really get the difference. To me it just seems like a really close friendship where you officially agree to spend tons of time together.
- Yes! This!
  
  This has been my feeling too.
  This may not be the direction you feel like taking things, but, my mindset settled on polyamory. I love that I can let friendships and relationships grow and blossom without any artificial limitations.
  I do hope you find what you're looking for

Can't answer the title question from personal experience unfortunately, but I can say, only you can figure out what your end goal is. Relationships are different with every person. So if you find someone you enjoy their company, you don't need to know beforehand what you want to do with them. It's okay to figure it out as you go.

I think for me, relationships are having a good friend with benefits.
I’ve had a few serious relationships and at the time I’ve felt like they’re the person I want to do things with, not ‘things’, just things.

What do you mean besides you know what, sex is by far the most important thing I want from a partner ... Better make sure you find someone who thinks like you lol

I'm not sure I have much to add here other then a little experience. I've had a date tell me "there's nothing there" and realized later that they wanted more than a friend. I am fairly old and have realized that I may not have much to give, romantically. That's fine! But you have to find someone who wants that, also. Myself, I am not really a dater. But if you can see that some people want something more than a friend, more than a friend and sex, you may find where you fit in. I am still working on that. Not easy, but I am also pretty happy on my own. It is good, and healthy, to work on you, and this post is part of that I think. Be well!

Do you want a relationship, even if it means you're only friends? Does sex have to be involved to make it a relationship?
- You're on to something here.
  Can a relationship even be considered a relationship if it is just friends? If it can, please explain how that works. I'm not pulling your leg here, I really want to know.
  Also, is sex a confirmation of a relationship or just an added bonus?
  I know I just answered your questions with questions. But that's why I'm here on no stupid questions.
  
  Similarly, what counts as a date?
  If I get a bottle of wine, make dinner with and get cozy on the couch with my best friend.. is that a date? Or are we just hanging out? What if we kiss?
  I feel like it comes down to intent, and if that intent is shared and understood. Which is why communication is so important in any relationship.
  I tend to take my friendships as seriously as my romantic relationships, because, often there is no tangible difference.
  I’ve had so’s that were asexual, I’ve had friends I fucked but never “dated”. I’m still friends with most of my ex’s. Sex is sex but the relationship depends on how you define it between the two of you. A label is a label, what matters is that both people feel comfortable with the dynamic and are on the same page as far as what the relationship actually is.
  Love comes in a myriad of forms and can evolve overtime, so often living in that grey area. Getting bogged down in trying to label and define what something is or isn’t will just make you rigid when reality comes and you’re in that grey area.
  A poster above responded with something about building into a common future which also helps differentiate but can’t really be used as a hard line. I’m actively working into a common future with my best friend and partner but I’m only dating one of them. Devotion, trust, respect, vulnerablity, consistency, and common morals/boundaries seem to be the things I look for when i’m looking at someone I’m considering to be a partner.
  
  You can have a relationship without sex, it kind of depends on what either person is looking for, but a non-sexual dating relationship is probably a bit rarer nowadays. Me personally, I have a high libido, if I’m dating somebody, I’m hoping it leads to sex at some point. That’s just me though, everyone is different.
  A sexual, dating relationship can be a sort of temporary phase of the relationship that usually transitions into something else. It starts off running hot, but it can either burn out (end) or things kind of die down and become like a candle (monotonous), or somehow they build the flame up into a campfire, or even a raging sexual inferno. It just kind of depends on the couple. Usually though, if it becomes a longer term relationship, then other things and responsibilities come into the picture (home, kids, finances, etc).

Definitely varies for people, and there is actually a book coming out soon called “The Other Significant Others: Reimagining Life with Friendship at the Center” that you might find an interesting read.
For me, my fiancée is my best friend. Sure we’ve both had best friends before, but the connection was instant and way more intense than with anyone else for both of us. What makes our relationship different than a friendship is that we want to build a life together, we’re a team, we’re each eachother’s top priority, and, yes like most relationships there’s a physical aspect to it, amongst other things. The phrase ‘she’s my person’ really encompasses what it feels like, personally anyway.
If somethings right, you’ll feel it. When you find someone that sparks a connection beyond just friends, you’ll know. And if that never happens, don’t be too hard on yourself and start thinking there’s something wrong with you. Being neurodivergent and on the asexual / aromantic spectrum can make these questions harder, if they apply. Just do what feels right and don’t over think it too much. Easier said than done, I know

It is very individual. For me, our first date felt like we've been hanging out forever already. I was super comfortable with them and vice versa. Bedroom compatibility helped, but I feel that 95% of that is they were my first partner to really communicate what they wanted. We also have very similar values in religion, politics, and how to approach life so there aren't any deal breakers. Similar taste in music helps too, we each introduce the other to cool new stuff but also have our own things the other doesn't like and we're respectful about that and avoid playing it when the other is around.
It's not all duckies and bunnies, we do disagree on stuff, but we're both reasonable humans who look out for each other so come up with solutions as they come up.