Fellow Linux noob, just started using it earlier this year so if someone with more experience wants to weigh in, please do.
That said, gaming on Linux is pretty good. Steam's proton makes most games playable out of the box, although it's still a good idea to check Proton DB to see if any particular game you want to play is playable.
As for your other question, I'm not totally sure what you mean by accessible and customizable, but I don't think any of your peripherals are going to be distro locked. The Arch Wiki is a pretty good resource for, well, everything, but most relevant to you for your peripherals (it also usually gives good information for any distro, not just arch)
If you're already paying for proton unlimited I don't see any reason you shouldn't go for it.
Also, forgive me if I'm wrong, but your post makes it sound like you don't know, you can just export all your passwords as a file and import them into proton all at once