Appeals Committee. Disputed situations in tournaments.

You can agree on whatever you want and however you want. On h3dm1, if it's HotA, then you can definitely upgrade vampires and place one-time boosters; if it's SoD, it's better to follow the rules of the tournament that was played on Mirror. As far as I know, there are no mandatory rules for Mirror other than the standard ХВ rules, and even then there are probably exceptions (for example, a red-rush might be allowed on L+U on Mirror if agreed upon)