Cook 1 pound elbow macaroni 2 min under package directions. Drain.
Melt 4 tablespoons unsalted butter over medium heat. Whisk in ¼ cup all-purpose flour cook 90 sec until golden.
Slowly add warm 2 cups whole milk and 1 cup heavy cream, whisking constantly. Simmer 4–5 min until thickened.
Add ½ teaspoon smoked paprika, ½ teaspoon garlic powder, ¼ teaspoon dry mustard powder, ¼ teaspoon black pepper, ¼ teaspoon cayenne, and 1 teaspoon kosher salt. Remove from heat, cool 2 min.
Add 8 oz Velveeta , stir until melted. Add 8 oz sharp cheddar and 4 oz Monterey Jack one handful at a time.
Combine sauce with pasta. Transfer to greased 9×13 baking dish.
Mix softened 4 oz cream cheese with 1 cup sharp cheddar. Spread over top. Scatter ½ cup Monterey Jack.
Broil on top rack 4–6 min until deep golden. OR bake at 350°F covered 20 min, uncovered 10–15 min.
Rest 5 min. Serve.