An old friend of mine had a huge QH that was a total king on the local circuit. Unfortunately, she had some confidence issues that prevented them from going much past that, but they were a force for a while.
I love going into an arena on an unexpected horse. I have a half Arabian half quarter horse that will clean up a jumpers arena no problem and half pass and bend prettier than most warmbloods. Not saying that warmbloods are not nice but they are definitely not the only breed that can go far in either world. I watched a 15.2hh Tennessee walker win a 3' jumpers class that was chalk full of warmbloods. Just depends on whether or not you are okay with standing out 😉
dressage is the basis for all riding, so every breed does dressage. the levels of dressage may differ, but it's the same general idea