Glad you found the docs!
It seems like we have to improve the website to better explain that remoteStorage itself is the protocol, while remoteStorage.js (which is what you found the docs for) is the official reference client library. Anyone is free to implement both clients and servers any way they see fit, in any language, on any platform, etc.. In fact, you don't need a library at all, if you implement the functionality in custom code. remoteStorage.js just makes it a lot easier, down to the point that you don't have to think about the protocol even.
Now, regarding the still-open questions: one simple example for how to use rs.js in an app would be the offical demo app My Favorite Drinks.
But as to the other questions, that's really a lot to ask, because essentially you want someone to post the curriculum for an introduction class to modern JS app development. I'll try to point you in the right direction anyway, but please keep in mind that a single comment on a forum is hardly enough to get pointers for what people take years, even decades, to learn.
This is exceptionally difficult to answer, because there are so many different options, and they also differ so wildly in their concepts. One popular option would be Facebook's React for example. But that just gives you the view layer, and nothing else. I personally am a big fan of having a framework that does everything else for me as well, so I'm using Ember.js. Then again, others swear on the simplicity and approachability of Vue.js.
But these frameworks only give you the tools to build the behavior of your app, and not the visual elements. That's a whole different problem category with equally diverse and plentiful solutions. I guess Bootstrap is still a popular choice, but that's just one option out of at least 10 good ones.