I believe formal nights are no longer true formal nights... the only place you need to dress up and follow dress code is Palos and Remy. For our 2 previous cruises I wore a suit and tie, and just changed out my dress shirt and tie for foral night, and palo dinner . My wife brought two nice dresses. They were made of a light fabric and didn't take up much room. Packing light is always a good idea...
On our first cruise I actually packed dress shirts for dinner, and realized it was not necessary..On our last cruise, the 14 nt EBPC, except for our Palos dinner and formal night I wore jeans and a dryfit polo shirt to dinner every night, and that was dressed,up compared to a lot of people.