>>384794985
from my time on an AMD potato:

update drivers including mobo
try making a gpu profile for vrchat inside your nvidia software. use multisample 4x instead of of supersample and set stuff to performance. 
disable any motion blur and frame sync in steamVR & nvidia

you could try this apparently it works on nvidia as well as amd
https://youtu.be/DpFvpUViJag
 
didnt do anything for me. native resolution was best.

launch vrchat at something low like 300p on your desktop projection.
close background stuff like discord
disable steam overlay and any other overlays.

maximize steam so its focused in the background while you are in game. 

download melonloader and get avatar hider mod, set it to like 5 meters