Tutorials and complete documentation are going to be there in MERN v2! Already, we have good enough number of comments in the code, and we are in the process of writing documentation. If you think any part needs more explanation, open an issue in Github. We will be more than happy to resolve it. One of the primary objectives of MERN is to make it as beginner friendly as possible.
Regarding the redux-saga, it sure is cool! I especially love that way it makes testing async actions easier. But, it is incredibly complicated for a beginner to understand. That's why we chose not to include it in MERN. But, MERN v2 cli can clone variants of MERN project (like MERN with Material UI, MERN with relay, etc.) which can include sagas. You can learn more about that here.