Give each one a nickname. When you add a game account you can name it, and that name is what you see when you place an order, so two accounts in the same game are never a guess.
Use something you will recognise later, like your in-game name or the kingdom number. You can add and name as many accounts as you like under Game Accounts.
Before you confirm an order, check the selected account is the one you want the packs in. We buy into exactly the account on the order, and once a pack is bought it belongs to that account. Neither we nor the game can move it to another one, so this is worth two seconds at checkout.