Joined: 12/31/69
I'm not sure if this will be the case where you'll be performing, but a couple years ago at the national NATS MT competition MT singers in the semi-final round were not mic'd (they did have microphones in the final round). This - coupled with the fact that NATS has historically focused on more operatic singing - definitely gave the advantage to classically trained VP folks and those singing more legit pieces. So one consideration might be to try to find out in advance if you'll be using a mic.
As with any arts competition, go for the joy of performing rather than with concern about winning, since art is by definition subjective.
Have fun!
Videos