Marinate chicken: Whisk together buttermilk, hot sauce, and 1 teaspoon Tony's in large bowl. Add chicken tenders and toss to coat. Let sit 10 minutes at room temperature.
Mix breading: In shallow dish, whisk together flour, cornstarch, 2 teaspoons Tony's, garlic powder, onion powder, smoked paprika, black pepper, and cayenne if using.
Double-dip tenders: Pull chicken from buttermilk, letting excess drip off. Dredge in flour mixture, pressing firmly. Dip back into buttermilk. Dredge again in flour mixture, pressing to create thick coating. Place on wire rack and let rest 5 minutes.
Fry: Heat 1½ to 2 inches oil in heavy pot to 360°F. Add 3 to 4 tenders and fry 3 to 4 minutes per side until golden brown and internal temperature reaches 165°F. Transfer to clean wire rack. Let oil return to 360°F between batches.
Make sauce: Whisk together mayo, sweet chili sauce, Sriracha, honey, ½ teaspoon Tony's, and lime juice until smooth. Taste and adjust seasoning.
Serve: Arrange tenders on platter. Drizzle with half the bang bang sauce. Serve remaining sauce for dipping. Garnish with green onions and sesame seeds if using.