what is best positioning in relation to the percussionist/drummer on stage?
IME/IMO, it depends. i play different genres at different gigs, and i'm not a singer. i can adapt, but i do have preferences:
- jazz gigs = better on the hi-hat side,
but,
- small/tiny stages = depends: maybe on the HH side, maybe in the center (drummers's right).
- large stages = depends vs. anyplace i'm assigned if there's good monitoring.
anyone can play anywhere if necessary. what we prefer is only that: a preference. hearing is crucial...
contributing is everything --- they work together.
for players who don't have much experience: be close enough to the drummer (physically, via monitors, both) to 'verify intentions' between bass and drums --- you gotta be working together even when you're not playing the same thing.
it's popular around here to say "lock in with the drummer" but the reality is that the drummer needs to be able to hear and follow/support and "lock in" with
you and me! i work with lots of drummers --- i rarely work
for any of them

...it's teamwork! many times i'm the expert and the drummer needs to hear me in order to play the most useful part. e.g., what side of the drummer helps the drummer understand what it is i'm doing to help him/her out --- and/or vice versa?