In Steam Deck Gaming Mode, if change the display mode and restart the game, there will be a "MenuBer" window. It leads to black screen or very low FPS. Change to the other window manually can fix this problem.
OP can play with GE-Proton7-44
Run winecfg to enable "Emulate a virtual desktop" and set "Desktop size" to 1280x800
If there is an error message about font when launching the game, manually add "Temp" folder under /home/deck/.local/share/Steam/steamapps/compatdata/1709590/pfx/drive_c/users/steamuser/ . Enable "Emulate a virtual desktop" to fix the problem of mouse click position in Gaming Mode with full screen.
Run winecfg to enable "Emulate a virtual desktop" and set "Desktop size" to 1280x800
If there is an error message about font when launching the game, manually add "Temp" folder under /home/deck/.local/share/Steam/steamapps/compatdata/1709590/pfx/drive_c/users/steamuser/ . Enable "Emulate a virtual desktop" to fix the problem with mouse click position in Desktop Mode.