Basically as the title says, with Proton 9.0-4 there is still a huge difference in performance. For exampl on Windows it just stays locked at 120 FPS in certain scenes with 50% GPU Usage. On Linux it's 80-90% for the same framerate and in many scenes it just drops to 90 or 80 FPS. Fortunaly my target is 60 FPS and for that same reason it's not an issue, but for people with worse hardware it can be a bigger issue.