Maps.me is a great one. You can download maps to use offline. And fairly simple to upload tracks. It even does routing offline. I also use Trailforks and Pocket Earth. Good to get familiar with them before you’re out in the woods
Locus and Gaia are both good. I've tried both and prefer Locus, but I think it's only available on Android. Locus has good maps available and you can also buy the BC Backroads Atlas through their store. Tons of features including track creation, gpx file import and full offline maps.