Opinion seems to be is split on whether plastic pressure barrels (PBs) are the dog's whatsits or a pile of dog's whatsit. They have the advantage of being convenient at packaging time and can dispense a super pint, but they are only really suitable for low carb beers like ales and stouts (not AIPAs) due to the pressure limits they have. But the biggest disadvantage is that they sometimes leak from seals (which is inconvenient but can be fixed) or worse they split and then become unusable. Some people would rather bypass them completely and go to cornies when moving away from bottles.
My suggestion to you is to stick with bottles and minikegs for the time being and then decide what you want to do next. And you don't have to buy bottles to store your beer you can use PET bottles that have previously held a fizzy drink like I do (although some brewers don't like PET bottles) or second hand beer bottles which will require a capper and caps unless you can acquire some flip tops.
Edit-
Now looked at what you have bought, which apparently includes a PB. Its obviously up to you whether you use it or not. But be advised its better to fill it as much as you can at the outset unless you can purge out the air with CO2 from a part empty PB due the spoiling properties of oxygen
And there's a long thread on your AIPA kit here
https://www.thehomebrewforum.co.uk/threads/youngs-american-ipa.45221
But be aware that at 19*C fermentation temperature it could take over 14 days perhaps 20 days before you can add the hops as I and others have found out. So dont rush it.