Recommendations for monitor arm(s)

Hey everyone!

I am kinda overwhelmed with info and cannot identify a couple of good options for stacking two 34 inch monitors. The price range is also so vast that I cannot really get which ones are actually good.

Budget is not an issue I just want a good solid choice that will hold both stacked and ideally is available in Germany/EU

Is it better to search for dial arms or 2 single ones?