A universal fits-all answer isn’t possible because it depends if you’re trying to avoid general pain or minimize nerve issues. It also may depend on which direction the disc is bulging or ruptured, since the nerves shoot out in different directions and more compression may occur on one side than the other. For my old (30 yes ago) L5-S1 ruptured/herniated disc, which now only creates sciatic nerve pain/numbness (but not pain at the site), sitting is still more comfortable but inching forward on the saddle puts less pressure on that part of my spine. That doesn’t feel as natural for me but it helps some. Spinning very light gears does not always help because you’re bearing more of your weight on your butt than in your legs.
In the last 10 yrs I’ve developed bulging or partial herniations at C-3 through C-7 (degenerative disc disease) which kept me off the bike for at least a year. The physical medicine doc who has done my epidural injections said I should never ride a bike again, but if I’m going to still try I should ride out of the saddle virtually all the time. We all know That’s not practical, but her point is that when producing power from your legs while sitting fixed on the seat, it keeps your spine more locked in place and leverages more stress on the entire spinal column. So I try to mix standing/sitting while climbing and also ride no-hands for long stretches on flat roads to take more pressure off my neck.
I can’t say for sure that also applies to low back disc issues—someone with an engineering background can probably talk more about weight bearing spots and stress displacement. All of that to say that there are some medical/ structural issues to figure out, not just changes in training routines.