I've used A LOT of different GPS hardware and software... the good news is, there's lots of options ranging from free to not all that much considering what you're after. Currently, my go-to apps are OnX and Gaia. Both are great. I've used Gaia a ton, so I'm pretty familiar and proficient with it. OnX is really on the gas and adding tons of features. I'm pushing myself to learn it and like a lot of the features. I especially like that it's really geared toward off-road. My easy button is a Garmin Tread Baja... mostly plug-and-play unless you're setting up location sharing which is super overkill (and incredibly expensive) for anything other than racing.
All that said, if you want the absolute best and up to daye USA mapping, you're going to have a hard time beating Lifetime Maps. Their detail is pretty amazing!