The doors open at 11 am for the first PAT and no guests are allowed in before that. Besides, a PAT is an arrive no earlier than time, so there is no reason for you to be there before your PAT.
Not really. Your boarding group number is tied to your PAT so you get the same one no matter what time you get there. I guess if you wanted to make sure you got pictures with the characters who come out into the terminal (at PC, not sure about other ports), getting there early might help?
There is the chance to check for upgrades (paid not free) plus just having the stress of travel over. I’ve always used DCL transfers from MCO to PC, those leave at 9:00 and get there around 10. They are the first in the terminal.
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