Whiz wit is the Philadelphia cheesesteak ordered with Cheez Whiz and fried onions, and the defining thing is what a pourable cheese sauce does that a slice cannot. Sliced provolone or American is laid on the meat and melts downward into it; Cheez Whiz arrives already liquid and is spooned warm over and through the chopped beef, so it flows into every gap in the pile rather than melting from the top down. The result is that the cheese is distributed, not layered. There is no band of cheese sitting above a band of beef, because the sauce coats individual shreds of meat the way a gravy would, and it stays loose and glossy instead of setting into a firm sheet as it cools. That coating behavior is the entire reason the order exists as its own call at the window.
The craft is the standard ninety seconds on the steel, with the sauce timed to a pile that has to stay loose. Thinly sliced beef is chopped and seared fast and hot so it stays pliable rather than going to rope, and the onions, the wit half of the order, are griddled down soft and sweet and folded through the meat so they are inside the mass. The Whiz is warmed separately and poured at assembly rather than melted on the griddle, which is what keeps it pourable; a sauce that thin does almost no structural binding, so the chopped beef and onion have to hold the sandwich together while the Whiz works purely as a flowing, salty, savory coat. The long roll is the structural component every cheesesteak depends on, tender inside and crusted enough to carry a heavy, greasy, sauce-slicked filling without tearing or dissolving. The whole thing is built and handed over fast, because a Whiz build is at its point while the sauce is still loose and hot.
The variations are the rest of the ordering grammar whiz wit lives inside. Whiz witout drops the onions and leaves the sauce alone with the beef. American wit and provolone wit keep the same fried-onion base and swap to a slice that melts down rather than a sauce that coats, which changes the structure and the sharpness entirely. Each is its own order with its own logic and deserves its own article rather than being crowded in here.