Can you play Captivating Poke Puff if your opponent's Bench is full?
No. It's public knowledge that you can't put down any additional Basic Pokemon on your opponent's Bench, so you cannot play the card.
Source: TPCi Rules Team (2016-08-11), TPCi Rules Team (2017-08-03)
If I play Captivating Poke Puff and find a Pokemon with the Omega Barrier Ancient Trait in my opponent's hand, can I choose that Pokemon to be benched or does Omega Barrier block the Captivating Poke Puff?
Yes, you can put that Pokemon onto the Bench. Ancient Traits are only active when that Pokemon is in play.
Source: TPCi Rules Team (2017-03-30)
When using Captivating Poke Puff can I choose to NOT put any Basic Pokemon onto my opponent's bench, or do I have to put at least one down if I'm able to?
No, you don't have to put any Basic Pokemon onto your opponent's bench if you don't want to.
Source: TPCi Rules Team (2016-08-11)
Captivating Poke Puff says to put any number of Basic Pokemon you find in your opponent's hand onto their Bench. Does this allow you to put more than 5 Pokemon on the bench?
No, Captivating Poke Puff does not allow you to exceed the normal limits of the game. You can put any number of Basic Pokemon onto your opponent's Bench up to the maximum size of the Bench.
Source: Steam Siege FAQ (2016-08-04), TPCi Rules Team (2016-08-04)
If I use Captivating Poke Puff and put one of my opponent's Basic Pokemon on the bench that has an Ability (like Shaymin EX's "Setup"), does the opponent get to use that Ability right away?
No, Captivating Poke Puff does not trigger any coming into play Abilities.
Source: Steam Siege FAQ (2016-08-04), TPCi Rules Team (2016-08-04)