The Nikkor 12-24 f4 zoom is a competent lens. I wouldn't call it spectacular but that is because I was used to using single focal length wide angles in the 35mm days. At the short end of the zoom range, it displays a strange perspective that is hard to describe. I call it lateral keystoning. If you want to shoot a building, as an example, you would expect the building to keystone from bottom to top as you tilt the lens from vertical. However, you would expect the sides of the building to remain perpendicular to the ground. This does not appear to happen at the short end of the zoom range with this lens. I am unable to get a right angle between the street and the side of the building and the angle becomes more acute as I tilt the lens from vertical. Just like a fisheye tends to bend these planes, the 12-24 tends to move them the same way without the curvilinear distortion. I hope that explains the phenomenon adequately. I'm bothered and disoriented by this perspective as I never encountered it in a wide angle lens before. I suppose one could call it "creative" but I just call it lateral keystoning.
Otherwise, the lens is fine. I don't see excessive corner stretching or softness at the edges. I don't see a change in image quality across the zoom range. I haven't tested any of the other lenses so I won't comment.
The 24-120 should be sharper than the 18-200 by a noticeable margin. I owned the lens in the pre-VR days and found it to be ok for a 5X zoom. I would venture to say it was better than most 5X zooms. It was cripplingly slow at the long end of the zoom range for someone like me who shot everything with ISO 100 transparency film, however, and I relegated it to use as an event lens to be used with portable flash.