I have 15% tints all around, and barely noticed a difference. If you can't drive iwth the auto-dimmers as is, then dont get your windows tinted. The difference is insignificant IMO. The auto-dimming featuer already darkens your view to the point where all you see is headlight, so adding a tint wont make much of a difference, as tints almost act like sunglasses; you will still see the lights.
also, i have no heard to being able to turn auto-dimming off.