I sit to sew. It's impossible for me to be in a balanced (neutral) position while standing and using the speed pedal. I used the OHSA guidelines to help set up my sewing & cutting stations -- I am 5'11" so I needed to raise up my cutting table on blocks because it was way too low for me. For sewing, I use a hardcover book with a roll of masking tape under it to put it at an angle so my left foot is at the same angle as my right (on the speed pedal).
https://www.osha.gov/SLTC/etools/sewing/index.html
In addition, I had a friend help me build this DIY sewing table so that I could have my machine flush with the table & as far to the right as I could get it. He also drilled a 3/4" hole in the front apron for my knee lift to fit through.
http://frommartawithlove.com/2012/10...able-tutorial/
Finally, I am currently building a suspension arm to help carry some of the weight of my quilt while I FMQ because even with a Slider, my neck still gets sore from having to move so much weight while quilting. And for my birthday I have asked for a used Steelcase Leap chair because I used to have one of those when I worked in a corporate office setting & it was so super comfortable for my legs, back & arms. Everything adjusted to the perfect height.
It's been a lot of work to try to get everything to where I can tolerate sewing for more than 5 minutes at a time, but I'm so happy to see the improvements. I, too, have severe pain in my low back, neck & shoulders. When it gets bad, it will radiate down my right arm & right leg. I've had more than a dozen surgeries & have made peace with the fact that I will be in pain for the rest of my life, but I refuse to give up my beloved quilting. It makes me so happy to make beautiful quilts; it's just a matter of finding what works. I tried the balance balls for a while, but found that while they were helpful for tailbone pain & low back pain, they didn't provide enough support for me (and I can only share my own personal experience based on my health issues) for my mid-back, neck & arms. In addition, because of my height, I couldn't find a balance ball that was high enough to maintain a 90 degree angle for my hips and knees so I usually would end up with more pain in those areas.
Since this is such a personal decision, I would really recommend you consult with your doctor & just try out different options. The one thing I would strongly recommend if you do go with a standing sewing station is an anti-fatigue mat. If you don't also have foot problems, typically going barefoot (or stocking feet or those five finger shoes) helps back pain. I used to work barefoot in my sewing studio & can say it really did help.