IIRC, PUP in the preseason basically means that you need to be cleared to play and taken off of the list to participate in team activities and practices. Once you get taken off the PUP list, you can't go back on in the preseason. I'm not sure what the benefit/rationale is for putting someone on the preseason PUP list, unless a team can have a limited amount of people in camp and they can look at other players instead.
Once the regular season starts, players placed on the inactive PUP list will have to miss the first 6 games of the season.
Bottom line, players on the PUP list for the preseason/training camp really has no impact on their status for the regular season.