Make the brine: combine water, kosher salt, honey, halved lemons, bay leaves, parsley, thyme, halved garlic, and peppercorns in a large stockpot; cover and bring to a boil, stirring 1 minute to dissolve the salt, then remove from heat and cool completely. Chill the brine in the refrigerator.
Brine the chicken: place the chicken pieces in a large container, pour the chilled brine over them, and refrigerate 8 to 12 hours (no longer to avoid over-salting).
After brining, rinse each piece under cold water to remove brine residue, pat dry with paper towels, and let sit at room temperature about 1½ hours until no longer cold.
Prepare the dredge station: whisk together flour, garlic powder, onion powder, paprika, cayenne, 4 teaspoons kosher salt, and 1 teaspoon black pepper; divide this dry mixture between two shallow bowls.
Place 1 quart buttermilk in a third shallow bowl. Add 6 tablespoons buttermilk to one of the bowls of flour mixture and toss with a fork or fingers until the moisture is absorbed and the mixture is shaggy; set up station in order: raw chicken, first dry flour bowl, buttermilk bowl, shaggy flour bowl, and a parchment-lined baking sheet.
Heat oil: pour at least 2 inches of oil into a large heavy pot and heat over medium until the oil reaches 320°F.
Coat and start frying thighs: dip thighs in the first dry flour to coat and shake off excess, dip in buttermilk letting excess drip back, then press into the shaggy flour mixture and transfer to the prepared pan.
Fry the thighs: carefully lower a few thighs into the hot oil, adjust heat to keep oil at 320°F, fry 2 minutes without moving, then continue frying 11 to 12 minutes more, turning as needed, until deep golden brown and 170°F internal temperature; transfer to a wire rack skin-side-up.
Fry drumsticks: while thighs rest, fry drumsticks at 320°F about 8 minutes, turning and checking for doneness (170°F), then transfer to the rack skin-side-up.
Increase oil temperature to 340°F. Coat breasts and wings as before, then fry breasts about 7 minutes until golden and 165°F internally, and wings about 6 minutes until golden and cooked through; transfer to rack.
Let rest: turn off heat and let all chicken rest about 10 minutes before serving.
Note: if you need to keep chicken warm, briefly reheat in a 400°F oven for a few minutes before serving.