Welcome to the community!
You can already use the alpha in your app, but there are of course still a few bugs (however, mostly with the new, seperate connect widget).
Also, the docs aren't finished yet. We're in the process of switching everything from in-repo markdown files and NaturalDoc code documentation to Sphinx/ReadTheDocs and JSDoc, rendered into a single, concise documentation website. This should actually be finished by the end of this week. (I literally have a pull-request form for most of it combined open in another tab right now.)
We're also aiming to release rs.js 1.0 beta by the end of the week. See this milestone: https://github.com/remotestorage/remotestorage.js/milestone/14
So, I'd say maybe wait until next week, and even if 1.0 isn't out yet, we should have proper docs for you, both for getting started as well as covering every detail of the public APIs.
Provider-wise, you can use the old and new rs.js with pretty much any remoteStorage server. Bonus feature in 1.0 is that you can also (optionally) offer your users to connect their Dropbox or Google Drive instead.