I've got a swopper (actual name - really) The base does not move but the stool rotates 360 degrees, bends just a little in any direction, height is adjustable but goes a little lower when you sit on it - which gives you a boost when you get up. I love it, but it was expensive ... I got all my sewing goodies in the 5 years before I retired. Now I only need to feed my stash monkey.
It does not have any back at all