Your duffle bag is no problem for the ship, you can carry on pretty much any of your luggage if you prefer. The airlines have very specific size and weight restrictions. If you're flying, be sure it meets with airline regs.
Your carry on has to fit through the x-ray machine at the pier. It's not as big as an airport machine. Why not put your valuables in a smaller carry on and just check your large duffle at the pier? It's carrying them off that makes the big difference. If you carry off you can leave the ship as soon as they release passengers. If you let them take it the night before, you have to wait till your ticket color is called.