I go about half by volume cream cheese to shredded Sharp chedder. You could use what ever cheese you like or a mix. I would say that the cream cheese helps keep the chedder from runing all over when it gets smoked.
Read around for a few different variations and see what you think appeals to you. I never do anything quite the same two times, but I do like sharp chedder and cream cheese for the base and then from there the filling can take on a life of it's own. Garlic powder, onion powder, honey, rub mix, shrimp, sausage, bacon bits, chopped pepper, whatever is on hand or what ever floats your boat. I must admit that I like mine cooked a little longer than most it seems, I like the pepper to be cooked to a softer state, but crisp is good too, if you just can't wait