A lock-off 2-bedroom is a studio and a 1-bedroom with an interior connecting door. The studio becomes the 2nd bedroom and will have a queen bed & sleeper sofa. The studio portion will also have a kitchenette.
A dedicated 2-bedroom will have 2 queen beds in the 2nd bedroom.
The lock-off will have 2 entrances since it's really 2 rooms. A dedicated will only have a single entry. If children will be sleeping in the 2nd bedroom, you would probably want a dedicated. If another family will be in the 2nd bedroom, a lock-off would make it seem like they have their own room.