I used to play Quakeworld tons back in the day, in the top UK Clan etc, the battle for FPS was ever present! (and low ping times). We mostly ran the software version until PC specs got quick enough that OpenGL was ok and it would never drop under 60fps etc
Anyway, iirc a couple of the best commands to speed up FPS at the expense of making it look mega ugly but at least giving higher framerate were
d_mipcap
d_mipscale
Probably defaulted to 1, set them a higher number, 1-10 I think. Basically removes most of the textures so looks ugly but big speed increase at least on the PC versions. I'm sure this will work in normal Quake but if not then just ignore me