As far as I can tell, the Cove Balcony's are on the Main Deck, deck 2. We have one booked on the Magic later this year and the Dream and Magic are sister ship's.
It looks like the 4J is an obstructed Ocean View all the way forward on deck 10. It's described as having a picture window. I think you would see one of the forward decks from your window, but I'm not sure.
I don't remember you ever mentioning motion sickness, but I'd avoid the 4J's :eek: !