Preheat oven to 375°F. Cook pasta 2 minutes shy of package directions; drain and set aside.
Sauté chicken in olive oil over medium-high heat until no longer pink, about 5–7 minutes; season with garlic powder, salt, and pepper.
Steam or microwave broccoli until just tender, then combine with pasta and chicken in a large bowl.
Stir in Alfredo sauce and milk if sauce seems thick; mix until evenly coated.
Transfer to a 9x13 baking dish, top with mozzarella, Parmesan, and panko if using.
Bake 15–20 minutes until bubbly and golden on top. Let sit 5 minutes before serving.