The cheesesteak supreme is the loaded build, and what defines it is not the longer ingredient list but the moisture problem that list creates. A plain cheesesteak is a fairly dry fused mass; the supreme adds fried onions, sweet peppers, and mushrooms, and every one of those releases water on the griddle. The sandwich is really a water-management exercise: three wet vegetables cooked down hard enough that they concentrate instead of flooding, then folded into the beef so the roll inherits flavor without inheriting a puddle. Get that wrong and it is a soggy sandwich; get it right and it is the fullest version of the form.
The craft is in cooking the vegetables down before they ever meet the meat. The mushrooms are given the most time, because raw mushroom is mostly water and has to be driven off until they brown and shrink; the peppers are softened until they slump and sweeten; the onions are taken to the same soft, caramelized state the griddle gives them on any steak. Only then is the thinly sliced beef chopped and seared fast and hot alongside them, and the cheese laid on while the whole pile is still on the steel so it melts through and binds beef and vegetables into one mass rather than a layered stack. The roll has to work harder here than for a plain steak: it carries more weight and more residual moisture, so it needs a tender interior and a crust with real structure to hold the load without tearing. Timing is the discipline, the vegetables cooked down in advance, the beef and cheese done last and fast, the sandwich closed and handed over before the heat has a chance to steam the bread.
The variations are the same supreme logic with the vegetable slate adjusted. The pizza steak adds tomato sauce and turns the build saucy; the pepper steak leans on long hots for heat instead of sweet peppers; a mushroom-and-cheese version drops the peppers and onions and runs the earthy note alone. The chicken cheesesteak supreme keeps the loaded vegetables and changes the protein. Each of those is a codified build with its own logic and deserves its own article rather than being crowded in here.