If you are in no rush, when you leave Charleston, just go down towards Savannah spend a day or three, then consider how far you want to go. If you were comfortable with hundred miles runs, why go farther or faster. You may run into a few areas that sites may get tough to find but if you plan your stops for 2 to 3 days, it's pretty easy with the apps like RVparky to find places to stop next. And you aren't rushed.
From what you said, you don't have to be anywhere at a particular time, so focus on the journey not the destination.