Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine the ground beef and ground pork with breadcrumbs, milk, diced onion, bell pepper, garlic, ketchup, BBQ sauce, egg, Worcestershire sauce, salt, pepper, and chili powder. Mix until well combined.
Shape the meat mixture into a loaf and place it in a loaf pan.
In a large skillet, cook the meatloaf in the preheated oven for 30 minutes.
While the meatloaf is baking, prepare the potato casserole. In a mixing bowl, combine the sliced potatoes, sour cream, shredded cheddar cheese, milk, garlic powder, onion powder, salt, and pepper. Mix until well incorporated.
After 30 minutes, take the meatloaf out of the oven and spread a thin layer of BBQ sauce on top if desired.
Pour the potato mixture over the meatloaf in the baking dish.
Return the dish to the oven and bake for an additional 30 minutes, or until the potatoes are tender and the meatloaf is cooked through (internal temperature of 160°F or 70°C).
Remove from the oven, let it sit for a few minutes, then slice and serve.