I am using an AMD Ryzen 5 3600 Processor and ASUS Dual GeForce RTX 4070 Ti Super OC Edition 16GB.

In steam, I use GE-Proton10-10 for the compatibility tool and for the launch options I have: PROTON_HIDE_NVIDIA_GPU=0 SteamDeck=1 gamemoderun %command% -PSOCompileMode=1

I found the PROTON_HIDE_NVIDIA_GPU=0 part to be what made the difference for frame-rate.

With a little bit of tweaking I got Marvel Rivals running with a higher and more consistent framerate on Pop OS vs what I had on Windows.

This was also with an Nvidia card.