a) The Remote Latency setting does not have any influence on chatting. It only ever plays its role when Studio engages playback (or record). Otherwise (when stopped), it’s in “chat mode”; you can adjust chat latency, but we recommend the default “auto” setting which tries to keep latency for conversation low.
b) The higher Remote latency, the better, because it gives the system more time to correct for connection problems etc. The only drawback is that Studio hat to wait longer for playback to become audible after start has been engaged.
c) sync is sample accurate with VST Connect unless it’s not set up correctly, in which case out-of-sync delays are very obvious (actually, in the range of the Remote Latency setting).