Preheat oven to 375°F.
Cook macaroni according to package directions until just tender. Drain and set aside.
While the pasta cooks, lightly brown the sausage slices in a large skillet over medium heat. Remove from heat.
In a large saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute.
Gradually whisk in milk until smooth. Continue cooking until the sauce begins to thicken.
Stir in the cheddar and mozzarella cheeses until melted and creamy.
Add garlic powder, onion powder, pepper, and paprika.
Combine the cooked macaroni, sausage, and cheese sauce in a large mixing bowl.
Transfer mixture to a greased 9x13-inch baking dish.
Sprinkle with remaining cheddar cheese and breadcrumbs if using.
Bake for 20–25 minutes, or until hot and bubbly and the topping is lightly golden.
Let stand for 5 minutes before serving.