We have been to the Norwegian Fjords on the Britannia previously and found the ship then to be not too overcrowded. We found the Caribbean cruise crowded. It was difficult to get a sunbed on sea days if you were not up early.
Trying to get a seat in the live lounge was always a great challenge.
The restaurants such as the Sindhu was heavily booked and we only managed to book in the Sindhu once.
The balcony cabins on the Britannia are not huge, but stylish and clean. This cabin is directly under the buffet and could hear the trollies above at times. It is partly sheltered from the sun but ok.