The key is to mix the cheeses so that you get salty and nutty from the Parmesan and Pecorino, pizza mozzarella with melt so nicely and provolone pulls them all together.
This recipe will make 2 Gluten Free hotdogs buns (4 little baguettes) or 1 traditional demi baguette. GF hotdogs buns will hold toppings better than any GF French style loaves you find in the freezer sections.
Carb counting this is going to depend on serving size and the bread product you use. Mornay has very few CHO as does the cheese. So, you might choose to count only the bread.