It is a continuous function, the acceptable parameters for temp and RH. Most folks go off VPD but ignore the infinite combinations to get said VPD. in other words, the chart 9/10 folks refer to is just a subsection snapshot of a much larger chart. Anyway, the pressure gradients in the air are much less important than the pressure gradients for your medium. As long as you aren't massively pulling water from your plants, then you really just need to make sure she is breathing okay...which is basically where VPD comes in. Just play around with it. Science go brr and math is fun.