All software is shipped with as few changes as possible from upstream, so I'm getting the software as intended. If there's an issue, it's likely due to the software, not my distribution's unicorn configuration.
Pacman. This includes PKGBUILDs, syntax, and speed.
Good support. For all that this distribution isn't "the standard", you find install instructions in places you wouldn't expect, and more difficult things tend to work on Arch more easily than on other distributions.
Easy to set new things up. Because Arch doesn't ship with much configuration, there's no existing configuration you need to investigate in order to wrangle it to work with something new. This is also a downside, but we'll get to that...
Inertia. I installed it a few years ago, and I kind of want to move to openSUSE or Fedora, but I'm too comfortable here.
Downsides:
You need to configure everything. That includes the security stuff like AppArmor and SELinux you don't understand.
Occasional breakages. Arch doesn't break that often, but it's annoying when it does. Usually visiting bbs.archlinux.org is enough to set you on the right path.
Some software is packaged more slowly than other rolling distributions. Notably, GNOME is usually packaged a few months after openSUSE and Fedora ship it.
Constant updates! And HUGE updates, at that! Not great for computers you don't use often. If you do, make sure to pacman -Sy archlinux-keyring before you install new updates.
I don't see any need for them! I like the defaults. I only change the keyboard shortcuts, and I usually don't even autostart anything. I tend to still install GNOME Tweaks so I can turn on Focus on Hover, move the Close button to the left side of the window, but I don't need an extension for any of that. I don't know what I would even use an extension for!
I use about ten different extensions that all add useful functionality, but the absolute deal breakers are 1) indicators for apps that require a system tray, 2) GSConnect to transfer stuff between my computer and my phone, and 3) clipboard history. I can't survive without those.
AppIndicators are a popular one. I have the extension installed for Fcitx (though I usually never touch it, instead using keyboard shortcuts). I previously used IBus for my input method, but because I often switch between GNOME and Sway, I've found Fcitx a better option. I so rarely use my phone that I don't need KDEConnect. And Fcitx has built-in clipboard history—not that I use it anyway.
I also wonder about Nix and Guix. But I never seriously consider Gentoo.
Are those really important thing I should have configured? The only safety thing I have is LUKS encription.
Ubuntu configures AppArmor by default, Fedora sets up SELinux, openSUSE also sets up SELinux to some extent—most major distributions except Arch do it, because you're installing it yourself. I recommend looking into it. AppArmor and SELinux are essentially about preventing privilege escalation. Here's a good place to start: https://wiki.archlinux.org/title/Apparmor
SELinux is an absolute pain to understand and setup, so it's good that Fedora does it.