1. Yes you can use your wallet and debit card for the transaction. Think of it as your buying a game on Steam, they let you use funds and a card to add more to complete the transaction.
2. Extra storage doesn’t hurt, but I think some people either add storage through a micro sd or add more storage manually by taking apart their deck and putting it in. Wouldn’t recommend taking apart your deck unless you know what you’re doing. It’s completely your call for storage