Route to can be a bit slow in offline mode
Often Prompts to use data when in offline mode
I use Maps.me to follow routes by bicycle that I create in Strava's route builder. Have crossed the US and used it throughout Europe. Great that I can add info to places I find along the way. Run it in airplane mode to get the most from your battery life and navigate through areas without data coverage.
Tried some other options but always come back to this.