You're talking about off-road driving I assume? For on-road GPS stuff, it is rare that I'm out of cell range long enough to be a concern (and I've traveled all over the U.S. for work these past 7 years).GPS is a not real high on the list but would be nice. I’m often out of cell range.
For off-roading, I've been using Gaia GPS with downloaded maps as well as AllTrails. AllTrails has a lot of good information for wheeling and OHV stuff and you can download the .gpx files easily (you will need a subscription, which is cheap and has paid for itself a few times already). Once you download the .gpx file, you can upload those files to Gaia GPS. I like Gaia for a few reasons - the mains ones are that it works in CarPlay and looks exactly like it does on the phone (with an identical interface) and it is also has the smoothest interface (I like simple for stuff like this).