I am a stomach sleeper. What do you recommend for softness or firmness?

To be perfectly honest, I don’t see any redeeming quality of stomach sleeping, from an anatomical perspective. However, if you sleep best that way and you wake up refreshed, your neck and back feeling flexible and aligned, by all means continue. The main thing is not to get a mattress that is too soft because your body can hammock. Most stomach sleepers do not use a pillow, or use a small one.