Using NativeScript I am developing applications both for iOS and Android, speeding the launch for both platforms at the same time and optimizing costs. I have also worked with ReactNative and can help with it given my extense experience with React ecosystem. Both NativeScript and ReactNative offer a way to build performant apps that runs smoothly in Android and iOS with the same codebase (one effort for both, with very little specific quirks). Resulting apps are not an "WebView" that renders a clasic html web applications, but a native software. That means access to the complete OS features, better integration and better performance than other frameworks such as Ionic. For those applications I can adapt for Angular and Vue.js, depending on your requirements I will recommend the best option. Also, the backend and API required for online service Apps is no secret for me, I can develop your existing or build it from scratch being it Node.JS, Elixir or Java.