We have a Garmin Nuvi and smartphone and hard copy atlas. Sometimes for fun, I will run both the GPS and Google Maps on the phone. Google Maps wins every time for total accuracy, but both have some quirks. Disadvantage of using Google Maps is that if you are somewhere where you don't have data service, you cannot update your route. The atlas is our fallback and has been used more than once.
I will have to check a truck stop for the motor carrier atlas, on Amazon it is closer to $50 than $20. I like the idea of knowing clearances, etc. in advance. There is one railroad bridge in Texas that I literally stopped and watched, making sure several 18-wheelers made it under, before I was brave enough to try it. I still grit my teeth every time we go through there.