I"m not aware of any forms you might have to sign regarding APAT using your details however, it is part of the terms and conditions of entry into the tournament that APAT can use them..so, basically, you have already given permission.
For DTD, you will need Photo ID...a passport of photo driving licence are the best options...I haven"t heard of anything else being accepted but others might know different. They might ask you to fill out a short form (I can"t recall) but it only takes a minute and you can do that on the day. Just turn up in good time.
I believe that the 6-max is NLHE.