Copilot GPS is excellent navigation and routing, and one can download entire country maps. North America, for example, is about 8 GB. In addition to roads, this app includes points of interest (gas stations, restaurants, parks, campgrounds, etc. with phone numbers and addresses) without use of the internet. So only GPS is needed once download.

If creating a route to follow or download a route with GPS waypoints, I would use Locus Pro or Mytrails.