Depending what time you plan on leaving NJ; We usually leave around midnight and travel down I95, which gets us past the DC-Fredickburg before the rush hour (plus I prefer driving at night - less traffic - less stress).
We take 3 days to get to FL - first night is around Rocky Mount, which is ~450 miles from NJ. The next day we drive down to the Savanha GA area.
IF - we leave during the day , then we tak 301 all the way to Richmond, more relaxing that I95 BUT can get hectic around Waldorf - it's all about timing.
We usually stay at a campsite for an overnight stop.
Gerry