I cant remember the type (I think it was either deluxe or something with aged cheddar in the name, but now that I think about it it def wasnt their nacho cheese sauce) but it was Bay Valley Foods Cheddar Cheese Sauce in a #10 can. And yup elbow macaroni.
To prep the noodles I would cook them right till the point as soon as they turn tender, not al dente but not mushy either. Then quickly rinse with cold water, drain completely, then a tiny tiny bit of salad/vegtable oil (so it doesnt stick) and store. Do not be stingy on the quantity of noodles for the pizza (you should see any of the cheese sauce), they’re cheap and its just not the same when they’re on the light side.