Apps like Gaia GPS can give you great granular detail. Earthmate less detailed but functional. If you use a lower zoom level in Gaia then it is pretty easy to download large sections of maps and have something equivalent as what Earthmate or this device will provide. Then you have a backup.
Maps.me is a great road app. I have used it countless times when plans have changed on short notice and I don't have cellular service. Pocket Earth is also very good. As mentioned you can download Google maps for offline use but I am no expert in that. Gaia is really working on improving some of its features which relate to overlanding. On my devices I have Gaia GPS, maps.me, Pocket Earth, iOverlander (I rarely use it), Ultimate Campground (I use this often), Earthmate (iPad for my InReach device), and I tend to use Google maps when I have phone service.
I still say devices like this pigeon hole you into what they want to give you whereas a smart device lets you choose. Don't like Gaia ok try Back Country Navigator. Don't like BCN well try something else, so on and so forth. Don't like you dedicated device, hope you can return it! Growing up before we had all of this "smart" stuff I generally don't find it too hard to go old school with written instructions and a printed map.
Finally BUY SOME PAPER MAPS! Delorme and Benchmark are good. I have a laptop bag filled with them along with MVUM paper maps and any other local maps that I have picked up at places. When all of your electronic crap fails you can easily use these map books. They are also great for planning around the camp fire.
Of course to each his own. Some folks just are committed to a single ecosystem. Whatever you choose learn how to use it! Take the time to read support files, how to's, user reviews, etc. You will end up getting a lot more use out of what you choose.
Good luck Garmin.