The line seems to run through North Carolina, dips southward in Tennessee runs pretty much down the Mississippi. No proper sweet tea in Texas.
If your waitress (scuse me, server) does not say "what y'all want?", then you are not going to get any sweet iced tea. LOL
As to the first point: Why would you ask? It would be as pointless as asking if you'd like butter and salt in your grits. Duh, of COURSE I would!
In the South, tea is made in its drinkable form. Just sweet enough to no longer be bitter. It should never be saturated with sugar (but, sadly, it is sometimes done). Coincidently anywhere there is good Barbecue, there is also good sweet tea.
As to BBQ: I have always noticed that the pig on the sign(there is nearly ALWAYS a pig on the sign) is an indicator as to how fancy the BBQ joint is. If the pig is wearing overalls and a straw hat, the food will be good and the atmosphere will be "rustic." If the pig is wearing a tuxedo and tophat, the atmosphere will look nicer than the food will taste.