According to the meteor docs, inserts block:

On the Server, if you don't provide a callback, then insert blocks until the database acknowledges the write, or throws an exception if something went wrong. If you do provide a callback, insert still returns the ID immediately.

So this would be wrong:

Meteor.methods({
  post: function (options) {
    return Stories.insert(options)
  }
});

I need to do this:

Meteor.methods({
  post: function (options) {
    return Stories.insert(options, function(){})
  }
});

Can somebody confirm that this is the case? The former will block the Entire Server until the db returns?

Yeah, it will block, but not the entire server.

In Meteor, your server code runs in a single thread per request, not in the asynchronous callback style typical of Node. We find the linear execution model a better fit for the typical server code in a Meteor application.

So, if you are worried about that it will block the entire server as it will do in typical Node, don't be.