I've spent some time around horses, and I think most horses realize on some level that they are much bigger and stronger than us. How that realization affects the horse's behavior depends on the horse's personality. Some are jerks.
Horses are roughly as smart as dogs. So you can train them up with a little time and patience. And you'd better, because they are giant awkward dogs who could fucking kill you with a single kick. And also they're prey animals so their first instinct is to think everything wants to murder them.