Combine coleslaw mix, pepperoncini peppers, red onion, mayonnaise, lemon juice, red wine vinegar, Dijon mustard, sugar, salt, 1/2 teaspoon granulated garlic, 1/2 teaspoon granulated onion, and lemon pepper in a large bowl. Toss until well combined. Cover and refrigerate until ready to use.
Place catfish fillets in a large shallow baking dish. Sprinkle hot sauce over the top and turn the fillets to coat.
Combine Cajun seasoning, flour, cornmeal, bread crumbs, 1 tablespoon granulated garlic, 1 tablespoon granulated onion, black pepper, and cayenne pepper in a large brown paper bag. Add catfish fillets and shake gently to coat fillets thoroughly.
Heat olive oil in a large skillet over medium-high heat. Fry breaded catfish fillets until browned and crisp, about 3 minutes per side. Place on paper towel-lined paper plates to drain.
Spread each hoagie bun with 1/4 cup remoulade-style spread. Place 2 catfish fillets on top and top with 1 to 2 cups coleslaw. Garnish with lemon wedge, cherry tomato halves, and banana pepper rings.