Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish with cooking spray or butter.

In a large skillet, add 1 tablespoon of butter or olive oil and heat. Add diced onion and red bell pepper. Sauté for about 5 minutes until softened.

Add minced garlic to the skillet and cook for an additional 30 seconds.

Reduce heat to low, add cream of chicken soup, cream of mushroom soup, chicken broth, 1 cup cheddar cheese, sour cream, paprika, salt, and black pepper. Stir until smooth.

In a large bowl, combine cooked spaghetti and shredded chicken. Pour creamy sauce over the top and gently stir until well-coated.

Pour the mixture into a greased baking dish, spread evenly, and sprinkle remaining cheddar cheese and panko breadcrumbs on top.

Bake uncovered for 25-30 minutes until bubbly and golden brown. Let cool for a few minutes before serving.