Putney school has a lot of what you describe… it’s pretty different and is definitely about fit. While you could glean some of that from looking at videos or reading the school’s mission. It won’t mean much until you are actually on the campus, and you would know very quickly if it’s the right place (or not 
My suggestion is try and visualize what kind of environment (you and) your son sees himself in, and see if that doesn’t narrow the search.