Before bed, I want to tell a quick troubleshooting story:
I switched to Wayland!
But DCS: World has a weird frame flickering issue.
I try Proton, doesn't help.
I try different Wine version, doesn't help.
I try messing with DXVK, doesn't help.
It's an NVIDIA driver issue related to XWayland.
I admit defeat and go back to X11.
But: Wine can be run in native Wayland mode!
I find out how to run Wine without XWayland.
It works flawlessly and more performant than ever before!