That is not more or less true than for a lot of genres. There are some reliable norms, some books that do them well, and also some damn quirky books that ignore all of them and still seem to be a western. I, personally [heart] paranormal westerns. i have been considering writing one but I think to sell it I should probably add a lot of sex (not that I mind). My only western so far is a gay romance. I made sure to have a horse, a gun, a town, a damsel sort of in distress, a villain and a good shoot out in it.