In addition to React Native components, you'll have access to the Expo SDK, a library that provides a wide range of native APIs on iOS and Android. Expo can also manage assets for you, handle push notifications, and build your native binary for submission to the app store.
Supernova V4 is the first true tool solely focused to close the gap between designers and developers for good. Studio allows you to import Sketch files and turn them into native mobile UI, adding animations, navigation, layout etc. in the process - as you like. Supporting iOS, Android and React Native with more platforms coming soon.