We just got back this week from an auto trip all the way across Kentucky (West to East and then return East to West)--auto trip but we have made these same routes with RV on earlier trips.
This may not be relevant to the OP question, but I'll add it anyway. Kentucky has had for some years a great system of "Parkways". on our trip we traveled the "Purchase Parkway" the "Western Parkway" and the "Bluegrass Parkway". On other trips we have traveled the "Cumberland Parkway." I may not have all these names exactly correct, but this is the basic idea. Noted on this trip that some of these are being incorporated into the Interstate system. Traffic was heavier this time than on earlier trips and a few more trucks, but nowhere near as on the typical interstates.
Once you get off these "freeways" the comments above by other posters exactly describes my own experience. Good surface but very narrow and winding/up and down.
We love Kentucky but trying to be honest in describing possible routes.