A friend and I were not sure when we decided to use Overconfidence for the game and we wanted to use ICWO on our teams. The problem is --- are we correct in guessing that when using ICWO on two agents....the only they can perplex up is their Attack Value, as instructed in Overconfidence?

Or can use ICWO to perplex defense, move, etc?

Overconfidence says nothing about Attack Value. You can still use Perplex on *any* ability, as long as it is only on the figure with Perplex (you can't Perplex other targets).

From Overconfidence Feat:
A character with Perplex may use it only on its own combat values.