Not keen on any of them tbh, but I’m not a fan of the NT’s installations that add nothing to the site they put them in. The garish ‘fort’ they stuck at the top of Housesteads a few years ago being a prime example. Want a viewpoint? Walk up to one on Hadrian’s Wall. Want to hear sounds of nature? Stand next to the Wall, close your eyes, put your phone away in your backpack for a bit.
If I had to choose one it would be the charcoal project, but far, far better to plant more trees in appropriate places and keep as many natural environments open for as many people as possible.