There are areas of Paris that are very quiet and not filled with tourist. If you ever wanted to go to Paris, I would say do that. I was only there for 1 night and could not get over the fact I was walking around Paris. I was there in the month of October and it didn't feel hugely cramped with toursit.
I was just in Bruges, so I can't say what it will be like in the fall but I can say this, in the summer it is over run with toursit. It is a nice town and it is very walkable. It may not be so crowded when you go, but I felt more like I was in a tourst town here than I did in Paris.
I didn't even put Burssels on my list because everyone I talked to, including my husband who was just there said they were disapointed with the city.
As for Copenhagen, I know nothing about the city so I can't really comment.