The spot allocation is not maily base on the size of the ship. For exemple last week, the NCL Joy was at Wharf 22 and this week the Wharf 30 was occupied buy a Viking. The Wharf 30 is where de new cruise terminial is located. So most of the ship doiing debarkation/embarkation acivities will be located there. Of course that's not and absolute rule, notably when there is 3, 4, 5 ships in town at the same time.
For the OP whenever there's a ship at Wharf 30, i see shuttles and HoHo buses in the area. And as princeton123211 pointed out there a lot to see in a walkable distance.
Welcome to Québec !