Put chicken tenders and peeled shrimp into a large gallon-size bag.
Whisk together olive oil, Italian seasoning, minced garlic, pepper, and salt, then pour this mixture into the bag with chicken and shrimp.
Seal the bag well and place it in the refrigerator to marinate for no less than 4 hours.
Fill a large pot with water, add salt, and bring it to a rolling boil; cook spaghetti until just tender, then drain and set aside.
In a large skillet, heat the marinated chicken and shrimp over medium-high heat for around 7 minutes.
Add thinly sliced red bell peppers to the skillet and continue cooking for an extra 5 minutes, then remove from heat and keep aside.
Heat 1 tablespoon olive oil in a large pot over medium-high heat; add diced pancetta and stir frequently until it crisps for about 5 minutes.
Lower the heat to medium-low and introduce butter melting it completely before whisking in the flour.
To the pot, add crushed garlic, parmesan cheese, heavy cream, and egg yolks; keep stirring constantly for about 5 minutes to create a smooth sauce without curdling.
Add the drained spaghetti to the sauce and mix thoroughly to coat all strands.
Transfer this creamy pasta into a 9x13 baking dish and spread evenly.
Arrange the cooked chicken, shrimp, and bell peppers on top of the pasta evenly.
Set the oven broiler to low temperature for better control on browning.
Combine shredded parmesan romano, mozzarella, Italian seasoned panko crumbs, melted butter, and garlic powder in a small bowl; mix well.
Sprinkle this cheese and breadcrumb topping uniformly over the assembled pasta casserole.
Place the dish under the broiler and cook for 5 to 7 minutes, until the top turns nicely golden and crisp.
Remove from oven and garnish with freshly chopped parsley before serving warm.
