On one of my Royal Caribbean cruises they strongly enforced the curfew, and on others it wasn't a huge deal. Everyone has had different experiences with it. Just be prepared for it to be enforced. If anything, go back to someone's room and hang out there until you're ready to go to bed.
Formal night is totally up to you. You will see everything from full blown tuxedos to men in khaki pants & a button down shirt. As long as you're dressed appropriately they won't deny you access to the dining room !
Future Cruises ❤
Carnival Elation - November 25 & November 30, B2B
Past Cruises ❤
Navigator of the Seas - 2005, 2007, 2009, 2010
Mariner of the Seas - 2007
Liberty of the Seas - 2008
Carnival Liberty - 2009, 2010, 2011, 2013 B2B
Carnival Miracle - April & June 2011
Carnival Dream - 2011, 2012
Carnival Glory - June & September 2012
Carnival Imagination - 2013