It may seem odd to start with the second step, but how you evaluate the first has a lot to do with the second.
Modern office chairs are generally fairly good as long as you are not among the 10% smallest or biggest size range in any body demension, and as long as you have no special physical needs. Most chairs have individual adjustments for any chair demension. This article focuses on the seat pan Adjusting your Seat Pan
Read the article and let me know what you think.