If you have tried the Cold Corridor Combat mod on Steam Deck you may have had issues getting it to run past the initial screen. The answer is to run it under Proton GE, I think I am using 7.5.

In terms of performance, what works for me to get a steady 45 FPS (I tend to limit my deck games to 45) is to notch down the resolution by one, use FSR to scale it back up. Set quality to Medium. Also set the Combat GUI scale to 1.5

Looks mint, very playable. Can be played at full 1200*800 however runs a bit hotter and will range from 41 to 45FPS.

Terminator shoulder cam obviously kills it, knocks about 20 FPS off whatever you scale it to.