I use Gaia GPS Premium as it has a wide variety of topo map sources you can choose from (and download locally) and good route capabilities. 3D maps - if well done - are good for a terrain overview but I never use them for navigation. Other apps are Topo Nomad and Pocket Earth - both of which I have -but my preferred app is Gaia. It's worked well for me hiking and mountaineering (but always have a map & compass as backup).