I hope this makes sense - the croup is the area from the point of the rump to the base of the tail. In your horse, and mine as well, this is quite short and the angle is steep.
See how the horse below is longer from the top of his rump to the base of his tail?
Where this mare is very short?
This is supposed to make for a rougher ride, but my horse has a short croup and it doesn't seem to affect him, he is a smooth ride. It would depend upon the rest of the horse's build as well, and I don't think it will greatly hinder the performance of your horse, if at all.
As for his goose rump, as far as I'm aware it doesn't affect performance, it just isn't real pretty. I don't think his weight will affect it much.
Overall I think you have a very nice horse!