Look at Carlo Biado who is the reigning world 9b champion - he puts his chin down on the cue for longer straight shots but the bigger the angle of the shot is the more upright stance Carlo uses. You can use both and still be the best![]()
If you look at this video you'll see generally taller stances. Not as tall as the real old time masters but taller than most pool and snooker by far.
In the old days all the masters also played Caroms Balkline, 3Cushion. Standing tall gives you better perspective of the angles. Coming down on the cue gives you better perspective of tip placement and precision aim on the OB. Generally speaking the hit on the OB in 3C isn't as critical in most cases as in pocket games. Of course there's many exceptions. Get low on those.
https://www.youtube.com/watch?v=wyw2PqRovL8