I have no idea how steep the interstates are through the more Southern routes (40, 75), but I have driven through Fancy Gap on I-77 a couple of times. It is a long climb up, but generally fairly gentle grades, with 6 laning on the slowest stretches and the scenery is nice. Now that would take you a fair bit out of your way tho.
If you turn on terrain on Google maps, I-40 looks to have some pretty steep grades, but avoids Atlanta. 20/75 doesn't look bad, but run you straight through Hotlanta.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2012 Chev Traverse LT with TP