A stand bag has -
ta da!
- a stand mechanism. When you lean it over a little, two legs pop out and it securely sets on three points.
A cart bag is bigger, doesn't have legs, and because it's designed to be placed in a cart where one side will be buttressed up against the vehicle, all the pockets and access areas are placed around the other 3 sides. They usually have stiffer walls and wider diameters than stand bags, so they're heavier. They'll stand up on flat ground ok, but they'll fall over a lot easier than a stand bag when not in a cart.
Pencil bags (or "Sunday bags") are fantastic for what you describe. They're light, convenient, and not so big in diameter that 2 or 3 clubs will be rattling around banging into each other when you lug it from the car to the range. As long as you don't mind laying your clubs down if there's no range-bay stand (and you don't need to stow more than a few balls and tees in the one pocket) these are a great choice.