I am using the trial version of CrossOver. I just updated to the recently released version.
I am playing Deus Ex GOTY Edition via Steam - with the preferred defaults it launches into a black screen with the menu music playing. Using Command-Q to quit isn't possible, so you have to Command-Tab to the macOS desktop to quit it.
Upon relaunching the game in safe mode, it works. The FPS when entering even mildly complex scenes hits 0 before recovering to a choppy 3-5 FPS.
In training, there were many sections where it would hit 0 FPS and then experience choppiness. Once 'complex' objects weren't being looked at and going around corners to reveal new content didn't happen as much, the FPS would shoot back to 30-60+ (very smooth).
Playing the first level hit 0 fps almost out of the gate. I didn't feel like it was going to be fun, so I stopped playing to report the issue here on the forums.
The last configuration detail I tracked down for the black screen bit (and maybe the performance issue too, can't confirm) was the 16-bit or 32-bit textures setting. It only works with 16 bit. Once you set it to 32 bit, it blacks the screen out.