Yes, if you moved all the cards that have this note type to a new deck, you can delete the other decks (if you don’t want to keep them). The V12 deck is the updated version and receives daily updates, so unless you have a specific use for the older cards, they are not very useful anymore.
Also, if at any time you think you deleted something unintentionally, you can always reset local changes: How to Reset Local Changes. This will restore anything missing from the AnKing Step Deck.