There has been a general agreement in cs performance guides and videos that you should cap framerate via nvidia control panel or via rtss, and also to use the start parameter"-noreflex".
However I stumbled on this video by CS2 Kitchen and tried the mentioned low input settings for a Gsync Off setup: using max_fps to cap fps (in my case ~300), removing -noreflex and turning reflex on in settings.
Yes, the testing in his video goes deep into input lag and not so much into frametime, however since I changed settings it does feel like not only my input lag but also overall gameplay experience has improved, so you might want to try this for yourself, if you used any those previously mentioned settings (maybe they're outdated?).
I recommend watching his video in full, since he backs up his data with actual scientific testing and it's quite interesting to watch. Hopefully there will be a follow up video about frametime. But so far I wanted to share this with you, since it was already useful for me and may apply to your case as well.