I think 'Game mode' as shorthand for no-post-processing is more of a TV thing, desktop monitors just have it as a preset for image adjustment controls. I have a couple of LED monitors with Game settings, and on both of them all it does is dial the sharpness up and crank the hell out of the contrast and saturation settings. Most monitor presets are usually way over-exaggerated, you'll likely get better results using the custom preset and messing around with the settings individually.