React Native doesn't make it so you share UI code between platforms (https://facebook.github.io/react-native/docs/platform-specif...). What you get to share is all the business logic between tailored UIs.

You can share UI code between platforms if you want, though!

At least Android + iOS. Some components are platform- specific but at least on a small simple app I've been successful sharing my UI code.

I haven't yet done any React Native, but it seems to me that hypothetically, you can share or not share as you go down the component tree. I can imagine dedicated layouts per platform, then shared widget clusters, then dedicated low-level widget implementations.

Yup, there is an entry point for both the Android and iOS app. You can point to the same root component or a separate one if you want separate layouts orwhat have you

Is it possible for tooling to maintain a lot of these quirks and then implement additionally on top of areas it falls short?