On the morning of the 20th, beginning at 6:00 AM, I traveled from Fredericksburg, VA, to Greer, SC in 8 hours - 442 miles, w/rest stops. Traffic was heavy from Raleigh-Durham on, but it never stopped, and only slowed slightly in the (lengthy) work zones.
I stayed with a friend in Greer, and on the morning of the eclipse, we drove down I-26 to Newberry. Traffic seemed rather light, but the rest stops were packed with eclipse viewers... bathrooms, snacks, shade, parking... perhaps they knew something we didn't?
We got to an eclipse party just southwest of Newberry and ~1 mile north of centerline, but left half-way to totality to dodge a rain cloud. Traffic south on 121 was light, with small eclipse parties all along the route. We ended up parked at a country store about 7 miles to the south of centerline and watched the event in a blue sky; the clouds also cleared up for the party we'd just left. A gasoline tanker pulled off and the driver got out to watch totality with us; he had planned this route in advance! Otherwise, we had the place to ourselves. I will state at this point, that at totality, we found ourselves standing beneath the bane of all astronomers: a street lamp. Didn't even notice that detail until it got dark; we just stepped off into the field a little more to get away from it.
After totality, we continued on backroads to Washington, GA, and my friend's observatory at Deer Lick, where we spent the night. We encountered no traffic of any consequence along the way, and next morning (the 22nd) we drove through light traffic back to Greer.
I stayed in Greer another night, and left at 6:15 AM on the 23rd for Fredericksburg, VA. Traffic on I-85 was heavy, with a rush-hour backup at the beltway around Charlotte, NC, but I still got home in 8 hours including rest stops.
I saw nothing anywhere along the way that looked like gas-price gouging, and the Internet only seemed slow on the weather sites as everyone demanded up-to-the-instant forecasts. We ate at Mutts in Greer on the evening of the 22nd and I can attest that there was no barbecue shortage, and it tasted fantastic!