Hi Pspa123,
I think you’re referring to this information:
There is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel” that may be useful as well.
Generally, the layers closest to your body will have the most dramatic impact upon comfort. If you have the ability to use a bit of a “softer” upper layer in a component system, this would be more noticeable than changing out a deeper layer. While all of the layers combined (including the covering) will impact overall comfort, changes “deeper down” in the mattress will have less of an impact in surface comfort, and changing out a core to one that is too soft could potentially impact your support, and then alignment. Using a topper or swapping out an upper layer is usually the more common way to increase surface comfort.
I hope that was the information you were trying to find. If not, let me know. B)
Phoenix