I have 3 maps apps with me whenever I travel.
1. Locus Pro. This is the Rolls Royce of map apps. So many functions(points, track recordings, overlays, navigation, weather integration, etc), and can also display online Google and other maps. Supports downloadable raster maps, and offline vector maps. Also saves and organizes points of interests and tracks. I use this most extensively when walking around on foot. Free version also available.
2. Google Maps. For vehicle navigation and searches. Offline maps available but not for some countries.
3. Maps.Me. Very nice detailed maps mostly from OpenStreetMaps. Also has navigation if you wanna ride or drive.