I can not attest to the MC-860 that your image seems to be from, because i only have the MC-812. The mechanism on the MC-860 seems a lot more flimsy to me than mine tbh.
As the price difference isnt huge, i would personally recommend going with the dual version MC-812 and just removing one of the arms (you can just pull these out of the socket on this thingy). That way you can also add another display later if you ever need it. You can also just rotate this 90° so it points forward, if you have symmetry OCD...

On mine i can rotate the display attachment part around all 3 axis just fine (unless i fully tighten the screws) and it still stays in place and doesnt move over time or anything like that. Idk if its really intended for that tho, so if you adjust it frequently, you will probably have to re tighten the screw from time to time or it might start to tilt forward just from gravity pulling it down.

It also has this fancy quick disconnect mechanism which is nice for attaching and detaching the display.
I also just found this one https://euroelectronics.eu/products/uchwyt-monitora-ze-sprezyna-gazowa-podwojne-mc-775
Another single arm version but with what seems like a more sturdy mechanism.