I use iwb and owb, depending on situation , kydex, a sticky, or cloth. That being said, sometimes the belly band holster is the best choice, pretty comfortable and can actually add some back support. To Mark438, when I want the least printing and the most comfort, a G43 in a bellyband at 3 o’clock is pretty comfortable and very unobtrusive. I have 2 bellyband holsters, one cheap, thinner, less support, good for a subcompact, and the other thicker like a back brace, with a couple mag holders.
Old back injuries, ribs as well, having broken 7 of them to go with the disc and vertebrae compressions and ruptures. These days, the bones aren’t too bad, but the muscles like to tighten and spasm, so I find an inversion table and stretching to be invaluable. Best stretch for lower back pain in my case is laying on stomach and resting on elbows. Takes some doing some days to get to there, but relief is in minutes.