We sail Oceania (Premium) the dress code for dinner is long pants like Dockers etc & a collard shirt
More casual venue is the Buffet
You do not need to share a table it is open dining show up during opening hours & be seated
Specialty restaurants are included but require a reservation
Non Alcoholic beverages included
you can get excursion packages for a fee
drink packages for a fee
Viking you get wine/beer lunch & dinner
basic shore excursion per port
dress code informal
SS I think required dress up for dinner but I would check the forums for the Luxury lines
Regent is all inclusive
drinks, excursions etc included
Dress code relaxed casual not sure on jeans & T's for dinner
Main stream line s you can usually wear more casual attire
then add on packages for drinks tours etc..
Everyone has different wants/needs
A good cruise TA could help find what you are looking for with your budget in mind
Happy hunting