I’m not about to tell you how to cook a hot dog, and I’m not going to tell you what kind of bun to stick it in, either; those are purely personal considerations. You heat up a wiener any way you find best, and stick it into whatever bun you like, but any weenie needs a warm bun. Just sayin’.
As to toppings, eschew French mustards; while France has been an ally since the dawn of our nation, putting Dijon mustard on a hot dog seems vaguely unpatriotic and approaches the epitome of pretension. Creole mustard is a laudable and appropriate compromise. Ketchup is acceptable in some circles (yes, mine) but if you slather mayonnaise on a weenie, you need therapy.
A relish is wonderful, and your favorite chili should always be an option. Chopped fresh onion is a must; use a white with bite. For cheese use mild cheddar, for chrissakes.