Place 1/2 cup all-purpose flour, 1 teaspoon of the kosher salt, 1 teaspoon garlic powder, and 1/4 teaspoon cayenne pepper, if using, in a shallow dish or bowl, and stir to combine. Lightly beat 2 large eggs in a second shallow dish or bowl. Place 3/4 cup panko breadcrumbs and 2 ounces grated Parmesan cheese in a third bowl and stir to combine.
Heat a 5 1/2-quart or larger air fryer to 400°F. Pat 4 tilapia fillets dry with a paper towel, then season all over with the remaining 1 teaspoon kosher salt. Working with one fillet at a time, coat in the flour mixture, then dip in the egg and let the excess egg drip back into the bowl. Coat the tilapia completely in the panko mixture and place on a large plate in a single layer.
Coat the top of the fillets with cooking spray. Arrange 2 tilapia fillets in a single layer in the air fryer basket. Do not overlap or overcrowd the basket, as doing so will cause the fish to steam rather than fry and won’t be as crispy. Air fry until golden-brown and crispy, 8 to 10 minutes.
Transfer to a serving plate and cover loosely with aluminum foil. Repeat air frying the remaining tilapia (check on them early, as they may cook faster). Season with more kosher salt if desired, and serve with lemon wedges.