So, this mopping with vinegar sauce - is that done throughout the smoke process, say every few hours then add some to the pulled pork?
In general, yes. If you want to try it, I think the mopping is important, but again, it's to your taste. Assuming you're not doing a whole hog, you control any amount of sauce you add after. Swimming in sauce isn't the goal, but the sauce provides much of the special flavor I think you're looking for. Remember, BBQ joints do very large amounts of que and take meat from all over the carcass. Pig-picking cooks, like
@Richard S said, get it right off the steaming carcass,and good ones will take from more than one area. The bark from rubs contribute, but I think the vinegar sauce is key.
But also remember that various regions use various sauces. SC is known for mustardy sauces, AL for their white sauces. (I haven't tried either.). Even NC tends to be divided by sauces without ketchup (east) and those with ketchup as a main ingredient (west). I recently saw an eastern NC guy strongly dissing any use of ketchup, while I personally prefer just a little and also have enjoyed Western NC BBQ. But vinegar plus red pepper seems to be basic in most along with other spices.
My favorite BBQ place is Allen and Sons which is only a few miles (fortunately

) away. I've tried to mimic their sauce (good luck trying to get the actual recipe), but I was a bit surprised to note just how much crushed red pepper is in the little cups they provide for adding to taste. Another favorite place is The Pit in Raleigh. They offer a choice of shredded or chopped. After having tried the shredded option, I asked our waiter which he thought was best and with no hesitation, he said chopped. So that's what I ordered and will now always order. The difference was striking, but I don't know if they treat the options differently in any other way.
Good luck and enjoy your research!