As the...semi-proud owner (he's destructive lol) of a QH Appendix I will tell you right now, he will not look the same when he's older. Joker (my appendix) changed looks in build, height and even color until the age of 6! He started out a rose grey, then had big dapples and now he's silver. Not grey, but silver. He shines like a nickel! Your boy here will look like a QH one day and then a TB the next and eventually, he'll decide on which one he wants to be! Lol also, if he's anything like my guy, that butt will shoot straight past his shoulders and then once his whithers catch up, his butt will shoot up again until he stops growing. Joker was 15.2 at 2yrs old and now he's 17h at 7yrs old.
Good luck with your boy! I like his color and he has a very cute face.