Rendering Resolution Disabled??

[LunaMoo]

Rendering resolution is only disabled when using software rendering, so if you have it grayed out it must mean you selected software renderer;p. RR also has no effect(but isn't grayed out) when using upscaling or supersampling post process shaders.

Also take note, rendering resolution above x1 will commonly cause glitches, whenever it's worth keeping glitches for the sake of sharper image is personal preference, but I would recommend to at least also activate reduce resolution for effects hack as it will improve bloom and some other effects in some games which otherwise look awful when render res is above x1.