Combine 1/4 cup sour cream, the mayonnaise, lime juice, cayenne, salt and pepper in a large bowl. Add the cabbage and cilantro and toss to combine. Cover and refrigerate until ready to serve.
Heat 1/2 inch of the oil in a cast-iron skillet to 345 degrees F. Lay out the fish pieces and pat dry with a paper towel. Sprinkle them with salt, pepper and 1 teaspoon taco seasoning.
Combine the breadcrumbs, flour and baking powder in a bowl and sprinkle with salt and pepper. Combine the egg, beer, hot sauce and remaining 2 teaspoons of taco seasoning in a second bowl. Dip the fish in the egg mixture, letting any excess drip off, and dredge in the flour mixture. Working in batches, fry in the hot oil, turning once, until golden brown, 3 to 5 minutes total. Remove with a slotted spoon or tongs and place on a paper towel-lined plate. Season with salt.
Lay out 1 tortilla on your work surface. Pile the following ingredients on top of each other in the middle of the tortilla in this order: 1 cup slaw, 6 pieces of the fried fish, a quarter of the avocado slices, a quarter of the crumbled tortilla chips and a quarter of the radishes. Smear 1 tablespoon of the remaining sour cream on the tortilla next to the avocado and add a few dashes of hot sauce; this will act as the glue to keep help keep everything together.
Carefully roll up the tortilla into a burrito and place seam-side down on your work surface. Insert 6 evenly-spaced skewers crosswise through the roll. Using a serrated knife, trim and discard the very ends of the roll (or eat them), and then slice between the skewers to create 6 skewered rounds. Repeat with the remaining ingredients.