I use one on my guy, he's never had much of a tail. You can get them in differnet sizes, from single to triple, he has a double and to be honest its not that thick/heavy. If a falsey is put in properly you shouldnt be able to notice it. As for the cut straight across/banged look, that can be achieved with a natural tail also, and is often done, in what I compete in anyway. Often when you buy a falsey, they arnt cut this way, so the buyer can cut it how they like.
ETA: When shad has his tail in, and its not been plaited, its looks as natural as the next horse