Marinate the Chicken: Add the chicken pieces to a bowl and pour over the buttermilk. Let them soak for at least 15 minutes to help keep the chicken tender and juicy.
Prep the Coating: In a shallow bowl, combine the cornstarch, flour, garlic powder, paprika, salt, and pepper.
Fry the Chicken: Dredge the marinated chicken in the flour mixture, shaking off any excess. Heat oil about 1 inch deep in a pan over medium-high heat. Working in batches, fry the chicken for 3–4 minutes per side, until golden brown and cooked through. Transfer to paper towels or a wire rack to drain.
Make the Bang Bang Sauce: In a bowl, whisk together the mayonnaise, sweet chili sauce, sriracha, honey, and rice vinegar until smooth.
Toss and Assemble: Just before serving, toss the crispy chicken in the bang bang sauce. To assemble the bowls, layer rice, mixed greens, cucumber, and carrot. Top with the sauced chicken, then finish with chopped cilantro and lime wedges.