“I can't really see as carrying over to hunting is where they predraw and have the draw hand pulling the string to even with the front shoulder before transferring to the back muscles. I may be wrong and I just need practice but it seemed weird to me.”
The video is totally about the effect of alignment, not transfer to back muscles. I believe John had already transferred to his back muscles when he drew the string even with his front shoulder. I don’t believe John would usually draw that way. He was just showing an out of alignment position he had inadvertently slipped into while trying to correct some other error he was working on. After he demonstrated the out of alignment position, he was able to move into alignment without having to re-draw the bow. The coach asked John if he thought he could move from his out-of-alignment position into the correct position, and John demonstrated that he could. I doubt that everybody could do that; I couldn’t. Your comment that it seemed weird is correct, and I think they would agree with you. However, it was helpful to me to observe the difference between John in an out of alignment position, and then in alignment. I think the point of the video is that there is more to shooting than using back tension; as Terry Green has long said, the key is alignment.
Sorry I really can’t answer your other questions. There has to be some increase in both draw length and speed by using proper alignment, but I can’t tell you how much.