I plan with Strava using it's popularity heat map (I road 9000 miles in 2019). I then cycle using my Garmin 520 bike computer, which is painful to use for directions, but up to the abuse particularly on single track, and I try to use memory based on previewing with street view and satellite photos while planning. I often have to backtrack, typically uphill. But most of the time I'm repeating rides, at which point I'm going off memory.