IMO, there is no advantage to using the plug under any circumstances -- it's aerodynamically insignificant.
On the contrary, I run the forward lines (one from each side) through the open drivewell as an insurance policy that the boat doesn't go anywhere. This allows a snug, but not over-cinched tie down so as not to compress the hull. the boat floats around a little but it will never go far if you run your lines this way.
PS If the drivewell is not suitably located, scupper hole(s) accomplish the same thing.