The height from the ground to the bottom of the ball will be determined by the trailer you're pulling, not the car.
The height of the trailer is such that the trailers hitch is horizontal with the ground, while the hitch receiver on all vehicles is attached to two points on the frame of the car, so the receiver height is fixed for the car - e.g my Subaru Forester has a lower hitch receiver height than a friends F150 by about 6 inches.
The difference in height is accommodated by the ball mount, which positions the ball such that you're pulling in a straight line horizontally through the trailer; you don't want a large upwards or downwards angle, as it will make reversing a lot harder. You can commonly get a drop of between 3/4" and 8" (and they are usually reversible, to get a rise); there are calculators on the internet if you want to work it out by math.
Unless you're doing a lot of towing of disparate trailers, you'll find that one ball mount and a couple of balls will be all you need.