Tiny difference in quality, you mention possession stats but not chances created, and of course you can't copy his tactics because you can't see them (but you can copy formation)

To answer your questions, there seems to be a possession penalty for OOP players (not sure of the %age), but possession advantage doesn't guarantee results. I guess nothing guarantees results. But you can improve your chances by (in order of impact, from my experience) bringing in better players, changing tactics and formations to suit your players, changing T&F to counter opponent, keeping morale high and keeping fitness high. Fairly obviously, if you try to do all of those things you'll maximise your results