Don't know if they're improved and/or which's good and which not, but few notes on those lower end ones. If there's leather, it's the worst of the worst scrap quality that won't last anything. Cushions can be utter crap, so be aware. I had some office chair from Ikea I reckon ~15+ years ago and the cushion just lost all of its shape in few years and I'm not even close to the 90kg region.
And the last obvious comment, the ergonomy is more than just the seat. If your peripherals are at an awkward position/height, your body will be in pain no matter what chair you get.