you'll always be able to play. If you sign up first, even if you're rating is lower, he won't be able to play without you playing. If there is a limit, such as only 5 players, even if you sign up but are out-rated, you would only be bumped to the lowest board
Why if I sign to a team match I can't play even if I sign before another player only because my rating is lower? I think that team matches spots should be avalaible only for the first players to sign in, not for higher rated.