Ubuntu 19.04 Radeon Linux Gaming Performance: Popular Desktops Benchmarked, Wayland vs. X.Org
With Thrones of Britannia and Warhammer II, two of the newer Linux+Vulkan game ports by Feral Interactive, there wasn't any real gaming performance difference to note.
With the lightweight Xonotic game, MATE and Xfce and GNOME Shell Wayland actually led to slightly better results but not something any gamers would notice as all the results were around ~250+ FPS.
When running the X-Plane 11 flight simulator, the only difference to note for this demanding OpenGL simulator was GNOME Shell on Wayland running slower than the X.Org-based sessions.