Peaks of Otter (approx. mi. 85 - 100) is the smoothest pavement with the best mix of curves and slopes. IMHO.
After your trip, please correct me if I'm wrong.
Down in N. Carolina, the Craggy Gardens area is also very nice (approx. mi. 340 - 350).
Anything from the high point (approx. mi. 430) to the bottom end is outrageously curvy and extremely entertaining.
It's difficult to pinpoint a favourite stretch of the BRP. It's all good.
Pick a happy, fun pace and stick with it.
In my experience, the only Rangers you're likely to encounter are those going the other way (impossible to predict) or those who tend to lurk near speed reduction zones.
Always consider that another rider might be pushing the limits of tire adhesion in the opposite direction so keep within your lane.
Ride safely, have fun and watch out for finger-waving slow poke Harley guys.