I have never used one before, but i don't think its a good idea using an identity card for a transaction over the use of bitcoin ATM, because as said by some, that you may be required for such once they discovered you're making a larger sum transaction, to your second question, Since you're having a direct ordeal with the company that owns the ATM, the requirement for each machine may be different form each other and also the country regulation could also serves as another thing to make it more complicated for privacy use.