I have a 50% tint on all windows and rear hatch and it cuts down significantly on heat in the summer, as well as protects the interior to some degree from sun damage. At 50% you can hardly tell from the outside that the windows are tinted, which was exactly what I was looking for. I think that is a more classy look.
Rear hatch is one piece. Tint film gets thinner as it gets more translucent. The shop I used would not apply anything lighter than 50%. Problem with rear hatch is that you need to be careful when closing it, as you can easily put a permanent smudge mark on the tint if there is contact between an item you are carrying and the hatch glass.
Ask around and find a good shop. The one I used was well-known and experienced.