What ergonomic adjustments actually matter in this price range?

Across the reviewers we read, the highest-impact adjustments are seat height, adjustable lumbar (both height and depth, not just a pad), and arm height. 4D or 3D arms and seat-depth adjustment are nice-to-haves that increasingly show up under $300, but specialist reviewers warn that more knobs don't equal better ergonomics if the underlying geometry is wrong for your body.