We were on Wonder in Jan. First week we were in CC with 4000 passengers from Icon (media, family members). Second week we were there with another ship (can't remember which one) that probably had 3500+ passengers onboard. We get off early (by 930) and have no trouble getting a chair anywhere we wanted. In our case by the pool. We're back in April on Vision with Liberty (I think) and we have Hideaway Beach passes for the day. Island can supposedly support 12000.
As far as Nassau goes, we've been there many times. Last time was a year ago. New port area is very nice, but limited food choices. We usually go to Senor Frogs for lunch and now with the new port area you can walk most of the way through the port and avoid the street.