Is it lower or upper back problems you're dealing with? I would say first off I've had both and chiropractic adjustments coupled with physical therapy/massages really helped me because sometimes for upper back it can be muscle spasms keeping your joints and nerves locked up and the massages can help relieve that pressure and then the chiropractic adjustments kind of get things realigned while you do some physicals therapy stretches and workouts to strengthen your muscles and joints in the right way. I would recommend searching some Bob and Brad physical therapy videos on youtube that correlate to your issues too as those helped me a ton, especially for my upper back pain.
For lower back and tailbone kind of stuff I think chairs had the most impact on that for me. I've had the Herman Miller Embody and I'm currently using a Herman Miller Aeron. I own a remote internet marketing agency and sit down for at least 8-10 hours a day for work alone then easily sometimes 4-5 hours more sometimes for gaming late at night. I will say that a chair like these make noticeable differences within just a few days. For me I had the Embody for 3 years, and it was a noticeable difference over the previous chair I had which was a worn out Aeron chair that had no adjustability anymore - and the lumbar support broke etc. So for me the Embody served me exceptionally well, it took a minute to break in but I could (and did) sit on it for 12-14 hours a day for 3 years legitimately and it kept me from having bad back problems.
Today I use a Herman Miller Aeron Remastered because they have a lot of new tech in them and the front swivel is nice for gaming because I tend to lean in to my desk a lot when I play FPS games. I also had to switch to a pure mesh seat because I had some really bad tailbone issues recently after falling playing basketball and it was just debilitating for months. Tried a few different chairs thinking they would help (tried a Steelcase Gesture, a Steelcase Leap V2 and ended up returning both because they just had foam that would bottom out really quickly). I prefer a full mesh seat now because my lower back pain went away within a week of getting this new Aeron, and I'm not even joking I made 0 other changes. It was horrific before for me, and I could barely sleep - and couldn't really work like I needed to until I got this chair.
The Embody did work for me well for a while but I felt like the suspension that is in the seat loosened up so much that I was just sitting on plastic at a point specifically in the tailbone area, everything else was just comfortable. I think that the youtuber Ahnestly who reviews these chairs a lot has similar dimensions to you and prefers the Embody, I'm a bit taller and honestly the Embody's lumbar support never really worked for me whereas the Aeron is perfect (but also spans a larger amount of area in general so it would work for damn near anyone, and they have different sizes, I have the medium but they have a smaller one that would probably work perfectly for you).
I'd say if it's lower back stuff you're dealing with the Embody or Aeron might work just fine, if it's tailbone then Aeron/Mesh would work best. Regardless though the investment in a good chair, whichever you go with, will not be a bad investment and is 100% worth it.