Drain the pickle chips in a colander for 2-3 minutes, then pat thoroughly dry with paper towels. Let sit for 5-10 minutes to remove as much moisture as possible.
Heat 2 to 3 cups (480-720 ml) of vegetable oil in a heavy-bottomed pot to 350°F-375°F (175°C-190°C), using a thermometer to monitor the temperature.
In a small bowl, combine the mayonnaise, ketchup, horseradish, and Cajun seasoning. Stir until smooth, adjust to taste, and refrigerate until serving.
In Bowl #1, whisk together the cornmeal, ½ cup flour, garlic powder, onion powder, smoked paprika, cayenne, salt, and pepper. In Bowl #2, whisk the egg, buttermilk, and hot sauce. In Bowl #3, place the remaining ½ cup plain flour.
Dip each dried pickle first in the plain flour (Bowl #3), shake off excess, then dip into the egg mixture (Bowl #2), and finally press firmly into the seasoned cornmeal blend (Bowl #1). Place coated pickles on a parchment-lined baking sheet.
Fry 8-12 coated pickles at a time for 1-2 minutes, flipping once, until deep golden brown. Return oil to 350°F-375°F between batches.
Transfer fried pickles to a wire rack set over a baking sheet to drain. Season immediately with a pinch of salt and serve hot with the dipping sauce.