Preheat the oven to 300 degrees F. Heat the oil in a small pot over medium heat. Add the garlic and cook, stirring, until golden, 1 to 2 minutes. Add the tomato puree, 1/2 teaspoon of the oregano, 1/2 teaspoon salt, 1/4 teaspoon pepper and 1/2 cup water.
Bring to a simmer then reduce the heat to medium-low. Continue to simmer, stirring occasionally, until slightly thickened, about 15 minutes. Remove from the heat and season the marinara with additional salt and pepper. Bring 2 inches of oil to 350 degrees F in a heavy-bottomed pot or Dutch oven, or set a countertop fryer to 350 degrees F. Line a large baking sheet with paper towels and set aside.
Put the flour, garlic powder, paprika, remaining 1/2 teaspoon oregano, 1 teaspoon salt and 1/2 teaspoon pepper in a shallow dish and stir a few times to combine. Crack the eggs into a second shallow dish, add 1 tablespoon of water and whisk until combined. Dredge each chicken tender in the seasoned flour, then the egg (allow the excess to drip off) and then the flour a second time. Fry the chicken in two batches until golden, crisp and cooked through, 4 to 5 minutes. Drain on the paper-towel-lined tray and season with salt as soon they come out of the oil. After the chicken is fried, fry the French fries and mozzarella sticks according to package directions, draining on the paper-towel-lined tray as they come out of the oil.
While the chicken fries, warm the buns in the oven, about 5 minutes. Rewarm the marinara sauce over medium-low heat until steaming. To assemble the sandwiches, put 2 chicken tenders in each hoagie bun and top with 2 mozzarella sticks. Top with a small handful of fries and then about 1/4 cup sauce. Add lettuce and tomato, if using. Serve warm with extra marinara for dipping on the side.
Adapted from (R)The Fat Darrell inspired by Darrell W. Butler, creator of (R)The Fat Darrell Sandwich, for Cooking Channel