Preheat oven to 350°. Cook macaroni in salted water until al dente, 8 min, stirring often. Drain but do not rinse. Keep warm.
Return pot to stove and melt butter over medium heat. Add flour and cook 30 seconds, stirring constantly. Add milk and half and half slowly, stirring until thickened.
Add all shredded cheeses in thirds until melted well. Stir in shrimp, sour cream, cheese curds, hot sauce, peppers and kosher salt.
Transfer to a buttered baking dish and top with toasted breadcrumbs, as well as a little more shredded cheddar. Bake until bubbly and golden, 15-20 min. Serve hot.