Never unhook for an overnighter!
Just park such that the trailer is mostly level.
Park farthest away from the front doors so the shoppers have prime spots.
If you arrive at night you will see other RVs parked. Park among them, but not too close.
You can do whatever you want inside your rv, even run generator, not a big deal. Be considerate that other RVs dont want to hear a gen right next to them, aim that gen away if you can.
Stay away from Semi rigs parked, they will run their motors all night and you will be miserable.
There will be signs posted on the light poles if you are not allowed to park overnight. Look for the signs.
Walmart doesnt care if you park, but sometimes the city will. In that case the police might ticket you, but probably just wait until 2am to knock on your door. In this case there will be nowhere to legally park overnight in the city, even private property such as walmark.
This is typically more a blue city thing, or a popular tourist area thing,might not even exist in SC.
Cracker Barrels also welcomes you and even have RV parking spots. Don't stay all day, stay at night, eat b'fast there then leave so to not block off parking spaces for paying customers.
Leave the truck stops for truckers who legally have fewer places to stay and are limited to how much time they can drive per day, unless there is specific RV/car parking spots that the trucks can't park in anyways. Truck stops are noisy all night and lit up like the sun - is a last resort