How to add a view inside a view?
The module 'Views Field View' that you have mentioned is very good imo. In order to use it, you have to edit a view A and add another existing view B as a field of view A. 

But this is as far as it gets, it does not facilitate a 'joining' of views of any sort, for that matter I think it would be better for you to rebuild a new view with relationships etc, if Views Field View is not adequate for you.