I don't know too much about all the southern routes, but when we did our trips to Disney we overnighted at Florence RV Park right off I95 in South Carolina: http://www.rvparkreviews.com/regions/South_Carolina/Florence.html Some of the more recent reviews (last we were there was 2011) are only mediocre, but it is within sight of I95 and has pull throughs (no disconnecting our TT).
It is possible to scoot quickly through New York City on I95, which is the quickest way "as the crow flies"... IF you can do it between roughly 12AM and 6AM. You may have construction, but it is usually not too bad. We usually plan to leave our house so that we go through NYC on I95 around 5AM, and usually(!) don't have any problems. We have been stuck at those early hours due to construction or an accident, so it happens. Any other times (and doesn't matter which days, sometimes weekends are worse) I wouldn't try to go through NYC. Having said this, the physical condition of the roadway is another story. Frost heaves and damaged road can make your camper bounce and bang all over the place. You go from brand new paved smooth road to moon cratered road constantly. Just the way it is! (so, after re-reading that paragraph, I guess I should have just said to go around NYC, lol!)