Well, Google maps has an offline maps option as well. Works great for most bike touring, let's you know when you need to update and is just plain easy. Gaia GPS is another app that can work well too. It will collect all sorts of data for you and there are tons of map overlays to help plan your adventure. The free Gaia GPS app is ok, but the premium is really where you get all the options. Then there is Strava, Ride with Me, Map Me, and a plethora of other apps.
Keep in mind battery life of tablet. In offline mode/airplane mode, with GPS on, it will still consume a bit of juice. For me, even with a Dyno hub, running GPS, and some pictures through a day plus listening to music my battery on my S7 will last almost one full day. A tablet has a bigger screen to power so battery probably won't last as long. I've tried it. If you are just pounding pavement that's fine. You should be able to find all sorts of places to charge up. Rural/isolated areas are different. Solar panels are great when you are stationary, but when moving are lacking alot of performance. Power Banks are great but add alot of weight.
Just a few things to keep in mind.
Enjoy the ride
