I've used OsmAnd and I like how easy it is to download map sectors locally and that it will do turn by turn on and off road. It has a bit of annoying niggle I've experienced on multiple phones (been using it since 2016ish) is that it won't close. You can force close the app and it still runs in the background. Still, it was free. If you stomach paying 20 quid Backcountry Navigator is perfect and has proper OS Maps.
Yku can stop google tracking you( not sure whow that works if using their maps but I ssume it just does not keep.a record ) but you would need to search online how to do it
Inise memory map.and its an app with maps downloaded to the device ( needs internet to do this) so works off line
You can pay annually( updates ) or a lifetime(.does not update) and 1:25 or 1:50 or both
I do the later and after 20 hears thebkdd new housing estate exists on roads but no issue off road
The massive advantage of OSMAND is that you can add to the map if it is wrong/missing information by becoming an OSM map editor. It's a great app and is privacy focused whereas Google will use whatever workaround they can to get your data.
To save Google maps offline, search for a place, the tabs at the bottom have a "more" option. Select "download offline map" and them move the map about and zoom in/out to get what you want. You can easily download all of Wales in one go for example.