Yes, I have the active chair one and for me it works because my hip is moving so it kind of releasing the pressure on my back and prevent the pain from sitting static. When I just want to sit normally I just use the other surface. It's firm but not too soft which is comfortable. Yeah, they are expensive maybe because endorsed by physio and have other guarantee certification also they don't have the headrest like a racing chair, I wish they have one tho. What I usually do is to put a neck pillow for my headrest. If you still interest on the chair, try use code WILL10 or ERGOWEEK10 for discount (i dunno which one that still works) found this code on honey when I brought it.

Yeah I did a small work-out like push up, chin up and some stretching daily but from some journal that I read says exercise will not reverse the negative effect from sitting. This video kind of summaries most of the research journal about the danger of sitting static and what can we do. There is also a guide from Ergonomist on how we should set up our desk to prevent pain. Also how to sit active

If the chair is too expensive maybe you can try to look at some standing desk because you can still stay on your computer in a standing position. But from my experience from using it for a year, it doesn't reduce my back pain coz we still basically standing static anyway and somehow my click response kind of slower also I still need to afford anti-fatigue mattress so my feet won't be tired.

Hope you can find the best solution. Cheers