I'm not sure if there's 3N. I think you meant 2D1Nor 3D2N.
For me, I orefer 3D2N because when I did 2D1N (due to weather), I felt a bit rushed. I didn't get a chance to relqx more on the boat.
During the afternoon stop, you can swim around the boat. They set up like a net at the back of the boat so that you don't get stung by jellyfishes.
As for the food, they will ask before the trip of your preferences.
Hope this helps