I am going to be honest with you because I feel that critiques on a horse's conformation should be accurate and not because a person wants to flatter the owner.
I'm sure he's a sweet boy, but he is a hot mess.
His neck is unfortunate. It attaches low into the wither and the muscles are developed incorrectly, so he has the start of an "upside down" neck. Until he's properly conditioned, it's going to be hard for him to use his neck for any of the rail events. Even then, his neck is never going to be correct -- it will always tie in low.
He is short in the shoulder in comparison to his hip and back. His back is fairly weak, which means that he is probably going to have a difficult time elevating his shoulders and rounding up to have the amount of drive needed to be successful in the western or hunt seat events. He will most likely always be a fairly flat (meaning through the body, not the legs) mover. With his shoulder, I would prefer to see a higher point to his shoulder and see it more laid back. A lower point of shoulder typically means the horse isn't able to use his shoulder as much for a free moving stride, and they are often choppy. It would be difficult to push him into a long stride for the hunt seat.
His back legs are significantly longer than I would like to see on a prospective rail horse, and the impression that I get is that it is going to be difficult for this horse to drive well off the hock. He gives the appearance of running downhill, and coupled with his weak topline and shoulder, I can imagine that he will be a difficult one to keep up off the forehand.
He is an attractive color, and it sounds like he has a nice personality. Do you have video of him? That would be the best way to determine if he has the movement to do the rail classes.
Regardless, even if he is not the nicest mover he may still make a good pattern horse.