Naio,
After several years of RV'ing - sometimes to obscure places (we're rockhounds) - we've found that there is no substitute for map detail and that it's best to not have to rely on Internet access. What this means is:
1. Use a satellite based navigator unit that you keep updated and that you also keep loaded with thousands of custom Points of Interest way beyond the stock ones that the navigator manufacturer includes with their updates.
2. Use superb ultra-detailed maps like those from BENCHMARK (an entire large format atlas per state):
https://www.benchmarkmaps.com/atlases
