My first crossing of the US was 29 years ago. I still have some similarities of using a blend of both paper maps and electronics to plan out the route.
Back in 1991/1992 I used a MS-DOS program named "Automap" to give me an approximation of the route. I even brought along a 80286 Sharp laptop on my trip. I used this to get me some rough approximations, e.g. if I wanted to go via Yellowstone, then roughly how far would it be and what major US highways would I take from the Oregon coast. Once I had the rough approximation, I would use paper maps on a day-to-day basis to see where I was and how I was following those routes.
So today, I will still get a rough approximation with Google Maps (auto directions with no highways checked) of general routes and I will still bring state highway maps. In general, I will have figured out the general route in advance of the day and limit my use of electronics as far as turn directions to either (a) sometimes more detailed corrections in a larger urban area e.g. finding a motel at end of the day or (b) reacting to some change, e.g. road construction removing the shoulders. In a selected cases, I might also use a bit more in advance planning such as checking Strava Heat maps for an urban area or peeking at a Google Street view to check general shoulders/conditions.
However, just as 30 years ago, I used a blend of some electronic tools and some paper maps, I still find myself doing some of the same. I still like to have something in my handlebar bag, either a folded map or some instructions I wrote down the night before - and use that instead of switching electronics to tell me where to turn.