Preheat air fryer to 380°F (190°C) for 5 minutes.
In a large bowl, whisk together flour, cornstarch, garlic powder, smoked paprika, salt, and pepper. Add milk and stir until a thick batter forms. Add cauliflower florets and toss gently to coat evenly.
Lightly spray the air fryer basket with cooking spray. Arrange half the cauliflower in a single layer, leaving space between pieces. Air fry at 380°F for 12-15 minutes, shaking the basket halfway through, until golden and crispy. Repeat with remaining cauliflower.
While cauliflower cooks, make the buffalo sauce: In a small bowl, whisk together buffalo sauce, melted butter, and honey (if using).
Transfer hot cauliflower to a large bowl, drizzle with buffalo sauce, and toss gently to coat.
Return coated cauliflower to the air fryer and air fry at 400°F for 3-5 minutes, until sauce is glazed and edges are charred in spots.
Serve immediately with ranch or blue cheese dressing and celery sticks, if desired.