The only choice is S, M, L etc. Baed on Champion System's website, I am a club cut, not a race cut!
There is only one cut for tri tops.
The club vs. race cut only applies to cycling jerseys - and those offered in the Gear Shop are club cut.
The tri tops are snug. If you are debating between two sizes and are "club cut", I'd probably go with the larger one.
Trying one on is obviously the best way to figure it out though. It's too late to do that if you want to get in on the bulk order, but if you can wait I bet there would be people at the upcoming club duathlon (March 10) who would let you try theirs.