I can't imagine that the seeds are already determined by Wednesday of Championship week. I'd have to think that the conference tournaments have SOME bearing on their seeding otherwise what's the point of it for teams that are already locks for the NCAA tournament.
For instance, if Iowa State is on the 2 seed line headed in to the Conference Tournament and they beat two of Arizona, Houston, Kansas and Texas Tech I'd have to think that it would be a resume booster. Also, teams on the bubble can absolutely lock in a bid with a quality win or two in the conference tournament, it's happened many times.