Vocals sound like Tool. Should be a blast to mix. Will volume be a factor in the judging?
While this isn't a mastering competition, so volume shouldn't be a consideration, a mix which is easy to master to be competitive will probably be a better mix, in the end. So, don't apply mastering to your submission, unless you're very happy with your mastered result! In that case, note that you did some mastering.
It's becoming a grey area in mixing. Many of us apply compression to the two buss while mixing, and possibly an eq, and a limiter. It's pretty much mastering, in the end, I suppose, though if you screw it up, it ties the hands of a mastering engineer to correct your errors.
My rule of thumb is to mix through a pseudo mastering buss, then remove that processing when exporting for mastering. But for references, I leave that stuff on.
I think if you make a note that you did or didn't do any two buss processing, Barry should be able to judge fairly!