toan3rd

If i understood it correctly, React Native basically gives you a JS runtime environment that handles communication with native APIs of the system and is shipped with your app. Flutter (and Dart) will transpile into native code and compile natively for your platform.

So on React Native you will have that abstraction layer add runtime latency and package size of your app, while Flutter (Dart) really outputs native code.

Have you tried codesandbox.io? It is in my view the most sophisticated online editor with live preview and a huge load of starter templates to spare you the build configuration.

It is my go-to solution for when i have an idea and just want to build it quickly anywhere.

There is experimental support to use VSCode as the editor, togglable in the options.