Whisk buttermilk and hot sauce together. Add chicken thighs, submerge fully, and refrigerate at least 4 hours or overnight.
Combine cabbage, mayonnaise, pickle brine, and chopped pickles. Season with salt and refrigerate.
Combine flour, paprika, garlic powder, salt, and pepper in a shallow dish.
Lift chicken from buttermilk, press into seasoned flour to coat both sides. Rest on a wire rack for 5 minutes.
Heat 1 inch of oil to 350F. Fry chicken 5-6 minutes per side until golden-brown and cooked through to 165F.
Pile fried chicken onto toasted brioche buns and top with pickle slaw.