I suppose that depends on your riding, just fitted one to the Crush today, it was the first mandatory purchase, I dont see why anybody would want to compromise the ideal seat position for either climbing or descending by keeping a post in one position all the way through a ride, and its just a pain in the rear to be stopping and raising/lowering the post by hand when required, the dropper was in my opinion (alongside 1x) the best trail riding innovation in recent years, I'd take the minor weight penalty any day, 200-300g?... hardly a game changing weight saving, take a **** before you ride, have one less pie... you get my point! But then i never have cared much for weight saving.
As for limiting max height? No not as far as i'm aware anyway, just got to do as you have done already drop it into the frame lower. You can limit drop height by fitting supplied collar, but max height is determined by rise length 100mm/125mm/150mm etc.