Hi sweetandsourkiwi.
Great to see that you’ve got so many helpful perspectives and good guidance.
gardenguy is quite right about different people liking different materials and feels… It all is very personal, there are a few more thoughts about the different specs that can affect how soft or firm a foam feels in post #4 here you may wish to peruse. The two most important of these would be the ILD and the compression modulus although there are also other foam properties that will affect the “feel” of a foam material as well outside of just its softness/firmness that are more subjective.
@ diynaturalbedding for chiming with helpful guidance. As always I appreciate your expertise 
@ NestHaven.
Thanks for your update and your helpful contributions.
I am happy that you are still sleeping Heavenly on your Nest mattress and that you are out of the “mattress searching loop”
Phoenix