Sounds like a Proton issue, try turning off Optimize Network for Speed or a different Proton build for the live version maybe?

hmm strange, this isn't helpful but wanted to share I am running Forever on PopOS with 7+ year old hardware fluidly both in FPS and Ping. not sure what to suggest besides trying alternative proton versions but I hope you can get it working.

I don't have any issues on Bazzite with my Lutris Battle.Net install.

I hope you are not cursed with opposite side of earth sharding issues....saw some people saying that was happening.

Hopefully, you're able to sort the problem out. I'd just like to reiterate what another user mentioned - SteamOS is really not meant for a desktop computer. It is made specifically for Steam hardware (steamdeck and steam machine) and other handhelds. They don't support it being used on a computer. They literally tell you this themselves too -

https://store.steampowered.com/steamos

"Users should not consider SteamOS as a replacement for their desktop operating system."

I saw another user give a great list of gaming-focused distros from Distrowatch and would highly recommend any one of them (Perhaps not Pop OS simply because their desktop Cosmic isn't quite ready yet for gaming, might be few releases off though hopefully). Personally I would recommend either Nobara or Cachy OS, have used both and both were brilliant.