Preheat the air fryer to 400°F for at least 5 minutes; lightly spray basket with oil.
Mix flour, cornstarch, taco seasoning, salt, and pepper in a shallow bowl.
Whisk eggs and milk in a second bowl; place panko in a third bowl and press cilantro into panko if desired.
Pat cod strips dry, dredge each first in the flour mix, then in egg wash, then press into panko to adhere.
Arrange fish in a single layer in the air fryer basket, spray tops lightly with oil, and air fry at 400°F for 8–10 minutes until crust is golden and fish flakes at 145°F.
Toss shredded cabbage with juice of 1 lime and a pinch of salt; mix mayo, sour cream, hot sauce, and 1 tablespoon lime juice for crema.
Warm tortillas in a dry skillet 20–30 seconds per side or in the air fryer 1 minute at 350°F; assemble tacos with fish, slaw, crema, avocado slices, and extra lime.