This is a great route planning tool that lets you make adjustments on how curvy you want the route to be. I've exported .gpx files of routes planned with Kurviger to Google Maps, and also to the Scenic app (iPhone) with pretty good success. I definitely recommend playing with it a little in familiar territory before using it on a grand adventure.
Route Planning 2018-05-30
Route Planning with curvi-ness selection and .gpx exportation