I just wiped my gaming rig (win11, 12700k, 7900xtx) and installed CachyOS a few days ago. KDE Plasma doesn't work, but Hyprland and Gnome do. I was playing Arc Raiders with a friend within an hour of starting the install. So far everything works, and it even sleeps and wakes without issue.
I've been using CachyOS with Plasma desktop for a long time now. Including my gaming PC. Zero problems. But I don't play any online games.
I love KDE, but it's too buggy for me. About once a day the bottom dock would just disappear. I really wish they'd focus a little more on stability.
I use Sway on CachyOS, and to me it's the perfect DE. Being able to switch between windows in under a quarter of a second indispensable once you've experienced it.
You'd probably want to use an X11-based DE like Cinnamon instead, many games still don't play well with wayland.
I did _exactly_ this 3 days ago after I hit a random keyboard chord on accident and brought up CoPilot (which I don't recall installing). I had held on to Windows for gaming just because I didn't want to fuss with Linux, but it was the straw that broke the camel's back. Instantly installed CachyOS onto a USB stick and formatted my entire drive.
I use KDE Plasma and it worked just fine. In fact all of my games (including Arc Raiders) are working just fine on Proton 10, maybe running slightly worse. The only issue I've run into is getting battle.net working through Lutris; I ended up manually installing it through Proton 10 on Steam and it worked just fine. Wish I made the switch earlier.