Recommendations for an iMac wall mount

I'm looking for a good wall mount for my 27" iMac. Dual arm for maximum adjustability strongly preferred. I've found options from $30-250 that can support the weight. What's missing are good photos & videos showing these products in action. And I'd like to have some idea if the less expensive options are really good values or just really cheap.

What I'm struggling with most of the photos of these are unhelpful when trying to decide how they will work in my space. So if you have photos or videos of these mounts as installed, please share! Thanks.