If i have mew ex (holon phantom) on bench that can see opponent's hand, do the attack of surprise or atonish choose opponent's card with or without looking?
You have to close your view to the hand before choosing again. It, at most, will give you an idea of what you're looking for. Them are allowed to alter their hand order to avoid losing their best card.
In other words, you can't cheat, use the see-hand power, and then Astonish any card you want away. You do the attack without looking. Yes your opponent is allowed to shuffle his hand so you don't just look at his hand and pick his best card.