tfung, Daybreak rooms are smaller than cabanas. They just look like a room with a TV screen.

Since both the Wing and the Pier are on the departure level, I don't know if you can go out without hassle. After arriving, you clear the security and go to the loung and then go back to the security and then to the passport control. Never done this at HKG.

Leaving luggage there until your flight is no problem, I think.