Pat the shrimp dry with paper towels.
Stir buttermilk and hot sauce in a bowl, then add shrimp and chill 15 minutes.
Whisk flour, cornstarch, cornmeal, panko, paprika, garlic, onion, cayenne, baking powder, 1 tsp salt, and pepper.
Heat oil in a deep pot to 350°F.
Lift shrimp from buttermilk, let excess drip, and toss in the dry mix, pressing to adhere crumbs.
Fry shrimp in batches 2–3 minutes until crisp and golden; do not overcrowd.
Drain on a rack or paper towels and sprinkle remaining salt.
Serve hot with your favorite dipping sauce.