When starting with ETXReaL, this heavily modified version of the ioquake3 that vastly improves the visual richness of Enemy Territory, was not affected by the three KDE test settings. The only exception was the Radeon Gallium3D performance of the Radeon HD 4870 going up when XRender compositing was in use over OpenGL.
The now defunct open-source Nexuiz game also improved with X Render on Radeon Gallium3D where as the two other driver configurations were flat across the board. While swap buffers wait was disabled, the Radeon Gallium3D driver configuration for this set of tests was hovering around 60 FPS except when X Render compositing was deployed.
With the very CPU-bound OpenArena 0.8.5 game, suspending the desktop effects for the full-screen gaming improved the results for the open-source Intel Sandy Bridge graphics and when using the AMD Catalyst driver.