I’ve studied shooting since I started coaching 11 years ago, here are my thoughts, take them for what you will:
Players need a good base to be balanced, but having them think about the exact width of their feet is counterproductive. As long as they are balanced and solid, they should be comfortable. Obviously change any glaring stance issues, but this something they often work out for themselves. The one thing I would pay attention to is having either a stagger or offset style, to improve forward/backward balance.
Personally, I think the follow through is the most important part of a shot. A bad follow through will destroy a shot regardless of the form leading up to it, and sometimes a good follow through can save a shot that had poor form up to that point. Locked elbow, hand finished to the rim, and what we call a ‘soft point’ to the ground with one or two fingers, to bring the wrist over. Be careful with girls, as I’ve seen a lot of turned, odd-angled hands on the follow through, which sends the ball offline, and with an unusual spin.
I teach power from the legs, shoot early in the jump to maximize power and lift, and a consistent delivery with the arm, regardless of distance.
One thing, with teaching younger players, especially girls who tend to launch the ball: have them lock their wrist quickly when bringing the ball up. This will get their hand under the ball, and produce a better arc for the shot.
Hope this helps. If it’s all BS to anyone, please let me know, I want to keep learning and learning!