The diagrams above are exactly correct. I would point out however that the stance ONLY supports the power unit! We teach the stance to get the proper posture so that the power unit is lined up correctly. Once proper power unit alignment is learned, then the support unit can be varied greatly to get the shot. The shooter knows what is needed to get the shot. Hunting, stumping or 3D seldom allow the luxury of a formal stance. We are on uneven ground, kneeling,squatting, you name it.
Beginners are usually taught the square stance but as they progress, we give them the open stance to get the "twist" from the pelvis to the shoulders that creates core tension and adds stability. In all cases, the shoulder alignment in relation to the target is absolutely of top importance for accurate shooting. Many times here, someone is advised to "open their stance" to prevent string slap. The stance has NOTHING to do with that!
An open stance will cause you to slightly tense your stomach muscles to turn your shoulders toward target alignment, a square or closed stance will probably not use those muscles to align the shoulders. Not a real problem if you know what is really needed at full draw for proper alignment.