PREHEAT AIR FRYER for 10 minutes at 400 F degrees. Spray basket with cooking spray.
GET COATINGS READY: Meanwhile add flour mixture, egg mixture, and panko mixture to three separate shallow bowls. Make sure each mixture is well-mixed.
DIP A FILLET on both sides into first the flour, then the egg, and then the panko shaking off after each coating and pressing panko into the fish at the end. Repeat with second fillet. Carefully place fillets into the fryer basket evenly in pan. Drizzle one side of fillets evenly with oil, if using.
RESET AIR FRYER FOR 10 MINUTES at 400 degrees F. Fry fish for 5 minutes. Gently turn fish over using a fish or thin spatula. Continue to fry another 5 minutes or until crispy and brown. If you’re unsure fish is done, cut into one to make sure it’s flakey and firm. (140 or so degrees F on an instant read thermometer; it’ll come up to 145 F as it rests.)
FIX BUNS/SERVE HOT: Meanwhile, divide cabbage and onion slices between the bottom halves of the buttered and grilled buns spread with mayo. Add a fish fillet to each and top with about ¼ cup guacamole and the other half of the bun. Serve hot with lemon wedges and potato chips.