Performance akin to Windows, if not better. I have played The Finals since season 1, and have approx. 300 hours at the time of writing. Switched to Fedora Linux around 150 hours of playtime. No noticeable differences.

I use CachyOS kernel with Fedora to squeeze a little more performance out of my machine. Not strictly necessary though. I have issues with my PS5 controller (bluetooth) when using Proton-CachyOS-9.0, so stick with Proton Experimenal.

Recently (mid-season 5), the game broke on Linux. The developers quickly fixed the issue though, to be fair. Switching to Proton Hotfix worked in the meantime. No issues playing season 6 on day 1. Highly recommend!