I didn't know React Native + Next.js was a thing? What is the goal of doing that? I don't know what problem Solito is solving, some helpful context would be nice for those of us who are foreign to the problem.
It's mainly cross platform components (Fernando refers to them as screens) that can be used on the web, iOS, and Android. In Next.js, you can import these components as pages. On iOS, file based routing does not exist. Solito fills in the cracks. His video at Next.js Conf was really informative: https://www.youtube.com/watch?v=0lnbdRweJtA.