I use short passing when I want possession and when I outnumber the opponent in the midfield. Sometimes its to dominate a lesser team or to hang in there v a stronger one. It doesn't require either DMs and/or AMs but works better with them. Note: it doesn't restrict pasing to short only it just sets short as a preference, your team will still kick it long if they decide to.

Mixed is what I use most of the time but I decide between the 2 for each particular match.

Long? - I've hardly used on my main and when I have I must've used it wrong because I've not been impressed by it. Used in on my former defensive counterattacking team and not found it to me any better than Mixed. And ofc players can still pass short when they decide to.