Found some Firefox forks but can't decide which one to use

Don't bother using Tor Browser or Librewolf as your main. They're fine as side browsers for dedicated use cases but as daily drivers, they're the direct opposite of fine.
Can't speak on Floorp or Zen but I do enjoy Waterfox for what it is. Not as strong on its privacy protections as LibreWolf is but way more usable.

I use Librewolf as my daily driver for most things, then Mulvad when I don't want any fingerprinting.
Mulvad is highly underated IMO.

Zen is a little too fancy for me and it may contain telemetry.
Haven't tried floorp, but seems promising (may try it later).
Tor browser if you want at most privacy with actual IP masking.
Librewolf is my favourite, it's fast and simple. Yet with good privacy features turned on by default.

Zen will give you the most functionality. Librewolf will give you the most privacy and security.
- Tor Browser will give you most privacy and security, but it can be considered overkill for everyday use. Librewolf takes second place.
  
  Well. I don't really think of TOR as a browser but I digress.

What would be a good option for the iPhone environment (changing phones not an option)? There are four different Tor browser apps from different developers. Using DuckDuckGo right now, but any other better options?
- Onion browser from Mike Tigas was recommended as alternative to official one for iPhone by developers. For normal browsers you currently have Firefox, Firefox focus and Orion from kagi. Those options are safest ones from what I know on iPhone
  
  Thanks, looks like the Onion from MT has quite bad reviews. Hmm.

Zen browser was my favourite but this put me off:
https://sizeof.cat/post/web-browser-telemetry-2025-edition/
- I'm pretty sure that they removed a lot of the telemetry in a very recent update, so I'm not sure how it stacks up now.

I was using (and really liked) Librewolf until I heard that they were having trouble keeping up with Firefox updates. Now I'm using the Phonenix configurations for Firefox and keeping the FF updates separate from the privacy configuration settings. Avoiding forks lets you get the best of both worlds.
https://github.com/celenityy/Phoenix https://codeberg.org/celenity/Phoenix/wiki/Comparison

Whatever you end up choosing, make sure it gets regular updates. Not being up-to-date with security updates/patches negates any security/privacy you get.

Mullvad browser is also another great Privacy web browser but probably be more suited if you have a active subscription to mullvad VPN since it's point is to blend in with other mullvad VPN users.

My setup is librewolf as main, ungoogled chromium as backup for problematic sites.

Anyone know of a desktop equivalent to IronFox?
- prob librewolf i use ironfox on mobile and librewolf on my pc and its very similar
  
  I meant more on the security front than UI, but Librewolf does mention "security" 5 times on their page so I guess they are probably more secure than base FireFox.

In terms of use, librewolf feels exactly the same as firefox. I chose librewolf but zen is my 2nd pick try them both.

I've been using Zen and Librewolf, I recommend both of them but Librewolf will give you the privacy out of the box. A friend of mine uses Floorp and he seems happy with it.

waterfox doesnt get regular updates, look at their github, theres one guy. (not specifically adressed to you OP)
i use librewolf and just turned some options on again so it doest delete everything when i shut it down.