I think that the confusion here is that there is a restaurant called Chez Queux on this spot, and during the tourist season they add an outdoor seating area, but for some reason that area is treated as a separate restaurant - they have a different menu, which does include nachos - that's my theory.
That outside place is called (by them) La Cave - I think.
That way the established restaurant adds a pop up area just for tourists - with a menu aimed at them (us).
Anyway, you can't beat the outdoor location during summer tourist season... perfect for a cold brew and listen to the outdoor musicians....
My wife and I had smoked salmon salads and they were really good with loads of salmon - they were under 14$ and I suspect part of the "real" restaurant's menu; so lesson here: good salads.
Also had a pitcher of a good local Canadian red beer for under 17$ - so that's also reasonable on a tourist area.
The outside seating area is on the Jacques-Chartier plaza, which is a great space to watch people and performers... the "real" restaurant kitty-corners the plaza.