In a large bowl, combine ground beef, sausage, breadcrumbs, 2 cloves minced garlic, salt, pepper, and eggs. Scoop mixture into 1-in meatballs and place on a plate.
In a large skillet over medium-high heat, heat vegetable oil and swirl pan to evenly coat. Add meatballs to pan and sear on all sides, turning occasionally with a tongs until meatballs are golden brown. Transfer meatballs to a clean plate.
Drain all about about 1 tablespoon of drippings from pan. Add shallot to pan drippings over medium-high heat and saute 2-3 minutes until tender. Add remaining garlic and cook 1 additional minute until fragrant.
Reduce heat to medium and add marinara sauce to skillet. Bring to a simmer, then add meatballs, cover pan, and allow to cook 5-10 minutes, stirring occasionally until meatballs register 165F.
Place split hoagie buns on a sheet pan and broil 1-2 minutes until a very light golden brown.
Divide meatballs and sauce between hoagie buns and top with cheeses. Broil subs an additional 1-2 minutes until cheese is melted and golden brown. Top subs with fresh basil and serve warm. Enjoy!