I currently use a combination of Ride with GPS and Google Maps to plan my routes. In fact, I'm doing that right this minute ... trying to finalise a 400 km route.
I like the two of them because Ride with GPS provides an elevation profile, cue sheet, and I can save the rides ... and Google Maps allows me more experimentation.
So I put in two points in Google Maps and have a look at the elevation, then I use Street View to check the condition of the roads and to check for signs and confusing corners.
If I like that segment, I'll map it in Ride with GPS.
I wish for 2 things while I'm doing this:
1) I would like to be able to see if a road is gravel or paved when I look at the map, without having to zoom in on Street View.
2) I would like to be able to hook Ride with GPS up to Strava. Now, as it happens, my wish may have been granted with this one based on a discussion in another forum. There might be an add-on that lets me do that.