If you want to learn Linux, Arch is the perfect balance between ease of use and DIY aspects. It now comes with an installer, but installing it manually will teach you the basics of how Linux systems are built and configured. It also comes with amazing documentation that makes it relatively easy to setup and once you do that, it doesn’t require much tinkering or changing stuff in order to use it.
Nix is pretty hardcore as for a new user. If you’re ready to learn entire functional language to manage it effectively then go for it, but I’d recommend something more traditional for first steps.
If you want to game casually, well in this day and age gaming on Linux is pretty good with most games running just fine. There’s problem with some popular online multiplayer games due to anti-cheat systems, but other than that mostly everything runs well with Proton or Wine.
Keep in mind that MacOS is also different than Linux despite also being UNIX-like. On Mac it’s all controlled by Apple, so things generally play nicely together due to tight integration and centralized development. On Linux many components are independent pieces of software that also quite often have replacements and you get different combinations of those depending on which distro you pick. Don’t worry, it’s also standardized to some extent, and while it’s not necessarily straightforward, once you feel comfortable (and you don’t face any issue with drivers/hw support), it’s really nice to use.