HEAT oven to 400ºF.
WHISK buttermilk and 2 Tbsp. each hot sauce and vinegar in large bowl until blended. Add chicken; toss to coat. Refrigerate 10 min., stirring occasionally.
MEANWHILE, place bread crumbs in shallow dish. Mix remaining hot sauce and vinegar in small bowl. Mix sour cream and blue cheese; refrigerate until ready to serve.
REMOVE chicken from buttermilk mixture. Dip chicken, 1 piece at a time, in crumb mixture, turning to evenly coat. Place in single layer on baking sheet sprayed with cooking spray. (Discard any remaining buttermilk mixture and crumbs.) Sprinkle both sides of chicken evenly with red pepper.
BAKE 20 min.; transfer to platter. Drizzle with hot sauce mixture. Serve with carrots, celery and blue cheese dip.