Preheat oven to 350°F (175°C).
Cook the jumbo pasta shells according to package instructions until al dente, drain, and set aside; toss with a little oil if not using immediately to prevent sticking.
Heat olive oil in a frying pan over medium heat. Add ground beef, breaking it up with a spoon, then add minced garlic and chopped onion. Season with 1/2 teaspoon salt and 1/2 teaspoon pepper and cook until the beef is browned and the onion is softened.
Reduce heat to low and add softened cream cheese pieces, garlic powder, onion powder, Italian seasoning, the additional 1/2 teaspoon salt, and the additional 1/2 teaspoon pepper. Stir until the cream cheese is mostly melted and evenly incorporated.
Stir in the triple cheddar shredded cheese until melted and combined, then remove the mixture from heat and let it cool slightly so it is easier to spoon into shells.
Spoon about 1/4 cup of spaghetti sauce into the bottom of a 2-quart baking dish to prevent sticking and spread evenly.
Using a teaspoon, fill each cooked jumbo shell with the cheeseburger beef mixture and place them open-side up in the prepared baking dish. If you have extra filling, distribute it around the shells in the dish.
Pour the remaining spaghetti sauce over the filled shells, spreading to cover them, then sprinkle 1–2 cups shredded mozzarella evenly on top.
Bake uncovered for about 30 minutes, until the sauce is bubbling and the cheese is melted and beginning to brown. Let stand a few minutes before serving and be careful—shells may be hot.