As I'm going to be a player, I've resolutely avoided reading the adventure portion of the PDF, so if this is answered there I can't check it.
Is the ship we start out on considered to use one of the ships in the Flip/Pack combo, and if so, which one?
The first adventure does make use of the Pirate Ship Flip-Mat, which is also compatible with the Ship's Cabins Map Pack. However, the Wormwood herself is represented by the tiles in the Map Pack. Other ships in the adventure are represented by the Flip Mat.