In the Carolinas the sauce on a pulled pork sandwich is not a condiment choice, it is a statement of where you are standing. The pork shoulder is smoked and pulled the way it is everywhere, but the dressing tells you the county: a thin, sharp vinegar-and-pepper sauce in the east, a vinegar base tightened with a little tomato into a red dip in the Piedmont around Lexington, and a bright yellow mustard sauce through the central part of South Carolina. The defining thing about this sandwich is that the sauce is the regional border made edible, and the meat is built specifically to let a thin sauce do that work rather than to be smothered by a thick one.
The craft starts with the cut and ends with restraint. Shoulder is used because its fat and collagen survive a long smoke and become the texture of the meat instead of rendering away; leaner pork goes to string under that much time and heat. The pull is left deliberately uneven, dark peppery bark mixed through soft smoke-saturated interior, so each bite carries both chew and give. Then the sauce is applied lightly and tossed through rather than poured over, because a Carolina sauce is thin on purpose: it is meant to season and to cut the fat with acid and pepper, not to coat the meat in a sweet glaze. The bun is plain, soft, and faintly sweet, chosen to disappear and to soak the thin dressing without falling apart. A scoop of crisp, acidic slaw goes on top, where it is structural as much as flavorful, the cold crunch and brightness a pile of rich soft pork has none of on its own.
The variations are the regional dressings themselves, each a codified build with its own defenders. Eastern vinegar-pepper is the leanest and sharpest; the Lexington red dip rounds it with tomato; the South Carolina mustard sauce is its own lineage entirely. The chopped whole-hog version and the slaw dog that runs the same flavors over a frankfurter belong to the same map. Each of those deserves its own article rather than being crowded in here.