The lower Mississippi really does not have much of a valley, though there are bluffs on the east side of the river in place like Natchez, and Vicksburg. Speaking of Vicksburg I would suggest taking some time to tour the battlefield park if you have a smaller vehicle you can drive while leaving the RV at a nearby camp ground. From Vicksburg south the east side of the river is much more scenic than the west side, and in general I think the Arkansas side is more scenic than the Mississipi side south of Memphis, though it has been a number of years since I last drove that section.
