Prof. Fatguy here with some information.
Cheesesteak: Steak, cheese. Add sauteed onions, mushrooms, and/or peppers to taste. Pat's and Geno's use Cheese Whiz, but the rest of the world uses American or provolone.
Pizza steak (my fav): Steak, cheese, pizza sauce. Add sauteed onions, mushrooms, and/or peppers to taste. Rarely does anyone use Whiz on it.
Cheesesteak hoagie: Steak, cheese, mayo, lettuce, tomato, onion. Served hot or cold. I've accidentally ordered one once (I had the flu and was too fevered to drive, and apparently, order a sandwich right) and it almost ruined my day with its mediocrity, but I've never seen anyone order one on purpose.
Chicken cheesesteak: chicken, cheese. Let's face it: Nobody you want to know likes this without pizza sauce or buffalo sauce, so it's usually either of those.