Hmm, spam click mode solves all speed issues as opposed to normal mode. Try spam click mode and see if there's a difference Also, mirror mode? If so, lower reaction time from 1000ms to ~100ms otherwise you will be a whole 1 second behind everyone (1,000ms extra ping/latency basically). Hold shift + F3/F4 to lower. If not using mirror client, ignore
Choosing a custom tile for mining: will be available in the next version, shouldn't take too long