Yeah, the navigation is a tricky thing in React Native. It is really important — how you will organize the navigation logic between screens, which screens are nested etc. For now I’m using react-navigation (https://github.com/react-community/react-navigation), but in future I’d like to use react-native-navigation (https://github.com/wix/react-native-navigation).
And about using Android SDK — there may appear some problems. For example — some external libs require 25 SDK version and the project still uses 24 version. Sometimes it can be handled in your gradle file, but what if your project will not work with 25 SDK version.