I'm looking at getting a new bike, but struggling with the most suitable one given the different geometries.

Given a particular torso angle, is there an optimal stack & reach? A large S&R would see the arms stretched out further in front, while a smaller S&R would see the arms pointing more down toward the ground. If too small, the knees would hit the elbows and if too large, one would struggle to take weight on the hands, but is there a parameter that would dictate the "correct" sizing?

I'll try to add an image soon to help clarify if needed.

Cheers!