A: Buttoned to the top? Most definitely not. Too reminiscent of Ed Grimley (albeit in a woven) or certain toolbaggish PGA tour players. Otherwise, Jay, you've basically got it. The Official Magnificent Bastard Polo Shirt Buttoning Policy is as follows:
Where n equals the number of buttons. A fully unbuttoned Lacoste polo (2 buttons) looks perfect. A fully unbuttoned J.Crew polo (3 buttons) looks a shade TTH, which is why it's displayed on their site in n-2.