I use Copilot RV
as my primary gps app while driving as it works offline and handles routing well.
I use Allstays for finding campgrounds and planning routes and finding Rest stops and Flying J's while driving. Needs a cell signal.
Google Maps as a secondary reference mainly for satellite and traffic, although Copilot does pretty well with traffic. Needs a cell signal.
I also use radarscope for weather, very useful while driving. Needs a cell signal.
The power of using a real tablet/phone is using multiple apps not just one.