What you would use ideally:
60hz refresh
gl_swapinterval 1
cl_maxfps 120, 90, or 66 (66 is ideal for double jumps, can switch to 120 for ramps, 90 for strafes and cjs, 27 for ladders and triples, 22 for standing djs/cjs)
cl_async 0 (i think client forces this anyways)
I had an issue a bit ago with awful response times at random points like you are having, I could have sworn it came up when I was playing the the cl_draw cmds, but who knows. I did a fresh install and I never had the issue again.
Does anyone know if cl_async can be set to 1(toggled on)?
I found out recently that it is a feature that the pro's use in the real Quake2 Jump servers so that when they lower their FPS with cl_maxfps, they don't experience the "choppy screen effect". However, they still have the advantage of using that specified capped FPS # to perform that specific intended jump.
I think what most of them would do is for any given map, they would toggle between two different fps caps maybe sometimes 3 or more for the entire map. so either like 66 or 90 for one map, and then another 120 66, or 120 90. i'm not 100% but obviously the more times you have to switch your fps in a map for certain jumps might drastically effect your finish time on that map. However I also think that's something the map creators will take into consideration when designing their maps maybe. I'm not too sure on all that map editing stuff but yeah xd
Also I'm not too sure about what FPS is good for what, but I heard that certain fps will make you strafe faster (bigger jumps) and stuff like that so yeah i think most, if not all of what ace is saying is right.
also a cool jump video by n00k!e i stumbled upon last weekish that is really cool you should all check it out. its called n00k!e 1337 miles per hour.
https://www.youtube.com/watch?v=goaEiIY0R-Yhe's most likely the best pure jumper Quake II has ever seen. pretty epic video too 19mins long. he makes it look easy though
good music too must watch!!
Also as Ace was saying, cl_async is forced to 0 by the client. I'm not sure why this is? or if it is just default and can be changed... hmm?