Whisk mayonnaise, sweet chili sauce, honey, and sriracha together in a small bowl until smooth. Refrigerate until needed.
Place chicken pieces in a bowl with the buttermilk and let sit for 10 to 15 minutes.
Combine cornstarch, flour, smoked paprika, garlic powder, onion powder, salt, and pepper in a shallow bowl.
Remove chicken from buttermilk, letting excess drip off. Dredge each piece in the flour-cornstarch mixture, pressing to coat evenly.
Heat vegetable oil in a skillet over medium-high heat to 350°F.
Fry chicken in small batches for 3 to 4 minutes per side until golden brown and cooked through. Do not overcrowd the pan.
Transfer fried chicken to a wire rack. Repeat with remaining chicken.
Place all fried chicken in a large bowl and toss with bang bang sauce just before serving.
Garnish with green onions, sesame seeds, and fresh herbs. Serve immediately.