I would like to know if I can manage user profiles and user authentication directly with getstream.io?
I had a glance at the samples and I don't understand how the users get created.
It's currently not possible to manage user accounts, profiles and auth within Stream.
Stream is best used in combination with an application (e.g. server-side Sails/Node.js, Python/Django, Ruby/Rails etc.) that handles these things and other functionality, application logic and services.
Your application will then have full control and flexibility over which users can read/write and be notified of updates to any particular feed.