Motors in parallel or in series?

Quick question …https://www.youtube.com/watch?v=3ZHCrXu3vus

**Great explanation… quick question… **

        So if you have 2 motors that are mechanically connected (ie.driving the same chain), you should connect them in series? By your definitions above that would allow them to in essense self balance the current…

        On a related topic, what would be the issues/benefits with using 2 motors this way to drive a larger load? Or would it be best to find larger motors? From an efficency standpoint…