Meteor Apollo and Meteor.loginWith<ExternalService>

I’d like to delegate customer authentication using external services such as; facebook, twitter, google …etc.

I this straight forward with Apollo? In Apollo’s Meteor documentation page it mentions

You may still use the authentication based on DDP (Meteor’s default data layer) and apollo will send the current user’s login token to the GraphQL server with each request.

Does this mean that using external services (Meteor.loginWith) needs authentication based on DDP?

If I’m using Apollo with different database, what does that me to Meteor.user() and other functions like that, and do I now have to manage the storing of user information separately in new database or does Mongo still need to be a part of the application because of how Meteor works.