The buffet area can wear what they want, it’s just the MDRs that should hold to a minimum standard on formal nights, some of the other ships have been letting things slide
I have lived in both Montreal and Quebec city and both are great places to visit. If you wanted to stay in Montreal and travel to Quebec city by train you can do it from $120 for two in economy class or $250 for two in business class. The business class comes with a meal drinks included (wine and alcohol are included for trips at lunchtime or after. I would suggest business class for you as it is one way and the seats are a bit nicer. There is a train that leaves Montreal central station at 08:36 and gets you into Quebec (Gare du Palais) at around 11:52. Check here for allowances Train baggage allowance | VIA Rail. We regularly take the train from Ottawa to Montreal and Quebec city and it is a nice ride. The Gare du Palais station is right downtown a 5 minute care ride from the pier.
You clear customs in Montreal, prior to flying on to Quebec city, you may not need to pick up your bags, you have to ckeck with your airline. Usually plan at least a 2 hour layover or a bit more if you can arrange it.