Compared to regional Chairman's...it's basically the same thing, only with a lot more teams to compete against :/
A list of interview times comes out around Thursday lunch (or it did last year) and then you can switch around with other teams, if necessary. As previously stated, two interview rooms--half the teams to one, half to the other. But as always, judges will walk around and stop to talk to you et al.
You can do the same presentation (funny story--one of the judges at Championships had been one of our regional Chairman's judges so she heard the same thing twice in one year...awkward
) or you can change it, it's entirely up to you.
It really is similar to regional Chairman's, just on a bigger scale.
Congrats and best of luck to you!