The aggressiveness thing is a myth and feeding in a seperate tub or in the enclosure is a personal preference just like feeding live or frozen. There are MULTIPLE threads on here of people going back and forth about what they like better and reasons why but it all boils down to what your BP and you do best with and stick to that routine.
I personally feed all three of my BPs f/t in their enclosures and the only issue I have had is my newest one acting weird while he was swallowing but that had nothing to do with where he ate. There has been no aggression and as a matter of fact my pastel has become very chilled out since I got him.
Best advise is to figure out how you like to feed your BP and stick to it. Good Luck