None of my Quarter horses were ever Downhill. Sometimes they appear butt high because of the big hips on them, but in reality they are not.
I have not met a QH that was not at least slightly downhill (functionally speaking - wither/croup level has NOTHING to do with whether a horse is level or not). I have met maybe one or two horses full stop that were UPhill! Even Hickstead was functionally downhill and he was a top showjumper. Not that I've met him, but I've seen loads of photos.
My gelding is level. That's the best most people can hope for, realistically. I have a lot of people tell me that Monty is uphill, he's not, he's just level with a moderate wither.
Downhill is a GOOD thing in a Western horse and considering QH are predominantly bred for Western disciplines one would hope that the majority are slightly downhill! I couldn't see a top Dutch Warmblood doing barrels, cutting, or reining, just the same as I can't see a QH (even the best of the best) doing top level showjumping/dressage/eventing. I have a friend whose mother has a QH that is used as a show hack and dressage horse, and is successfully competing Advanced level dressage (I think that's roughly equivalent to 4th?), so I know they can and do break breed stereotype. I also know that this particular QH came from a farm that specifically breeds for horses that can do either English or Western with success.
My mother's QH is the most level I have met, including friend's mother's dressage horse (says a lot for the training of said dressage horse), and he is still slightly downhill, functionally speaking. His wither is a lot higher than his croup (he stands around 16hh at the wither, maybe 15.2 at the croup) but he is still functionally downhill.
This foal's movement is quite downhill, he doesn't look ridiculously butt-high standing still but if you look at him in the canter it's a different story entirely. Doesn't matter over much if OP wants to do western with him, or a bit of lower-level dressage. If they are naturally wanting to move downhill/on the forehand, without a rider on their back to throw them off, then they ARE downhill.
Final word, my filly is quite butt-high at the moment and she moves level to uphill ALWAYS... she should mature level to uphill, going on her sire and dam and half-siblings.
The movement is ALWAYS the key.