Thanks for telling us the ship you'll be sailing -- that makes a huge difference as different cruise lines might have different policies and amenities.
is the FAQ page for your cruise line and ship. One that jumps out at me right away is that the ship is on 220V power -- so you will need a converter for your U.S. electronics. Also, hairdryers are not provided in the cabin. You will need to go to the front desk or ask your cabin steward for one.
Regarding luggage, you can bring a carry-on bag onboard that contains medications, other valuables, or items you will need right away. We have a small carry-on for this purpose.
Your cabin steward can supply an extra blanket or two, if needed. Also -- be assured that your cabin won't be below the waterline. There are several decks below the passenger decks, that are not marked on the deck plans as they are for crew only.