This is similar to the single add-on monitor mount but setup for triple screens. It can also be used as a single monitor mount if you don't currently have triple screens available and may upgrade in the future. It connects to the uprights of the rig. Placement is limited, but it is usually easy to achieve appropriate placement if you are happy with monitors reasonably close and to make a view that approximates reality.
I would not recommend this for the basic rig, although it should be fine, the Plus has more inherent stiffness that. I have not personally tested with the Plus, but I have had good reports of similar models that I have shipped out to customers.
It should work with any screen size up to and including 32" and maybe bigger.