It’s difficult to generalize as it really depends on the sandwich. Too much is too much, too little it too little. Certainly, a sandwich shouldn’t be difficult to eat. As said above, a grilled cheese is often a pretty short thing.
I’ve never been a big hamburger guy. I like them fine but usually other things are more tempting like a Reuben at a restaurant or a bratwurst at the cookout. However, I’ve lately made a few batches of ‘Big on flavor, not in volume’ burgers based on a video I caught by Kenji (love that guy). https://www.youtube.com/watch?v=yUG9ZXhJEbg It’s not really a recipe but more of a technique. It calls for smaller patties, 3 ounces or about 80 grams each. Work the meat more than usual for a burger (it’s gonna be thin) and then flatten out in parchment so that they’re bigger than the bun. These wind up being the perfect size for the very cheapest, store-brand buns. Generously salt and pepper and cook over lump charcoal. I’ve been keeping the toppings to a slice of onion, a slice of tomato and some spreadable condiments, it’s a very manageable sandwich.
French dip is somewhat adjacent to our Chicago hometown favorite: Italian beef. I also have some ‘rules’ for what shouldn’t be on a beef. No cheese, no garlic bread, no barbeque sauce (gak!), pick either sweet or hot peppers (not both), and I don’t personally condone the combo which is beef and an Italian sausage though a lot of people go for it.