Hi aminah,
The further away from you a layer is the less effect it will have on the overall feel and performance of the mattress. all the layers of a mattress compress simultaneously to different degrees but the force of compression both spreads out as it travels through the mattress and some of the force is also absorbed and dispersed through the mattress (the amount of energy that is absorbed by a material is called hysteresis).
This means that the heavier you are and the thinner the mattress the more the lower layer will have an effect. For most people it would have little noticeable effect at all but for some people it would have more of an effect. Shawn’s comments would apply in “most” cases while FSF’s comments would apply in “some” cases.
The thickness of a “comfort layer” or “comfort zone” as well as the thickness of a mattress itself will affect how a mattress compresses just as much as the ILD or compression modulus of the materials. All of these and how they interact are part of how a mattress provides pressure relief. If a mattress has 3 layers that are M/F/XF … then the 3" medium layer would often be too firm for someone that had a lighter weight and could create some pressure point issues even though someone with a heavier weight would compress it more and it would feel softer, distribute weight better, and provide better pressure relief. If you have two medium layers on top … it would provide a softer and more pressure relieving surface for someone who was lighter. As the post I linked mentioned … thicker layers can compress to a greater percentage of their height before getting too firm and compress more gradually and are more adaptable to different body types and sleeping positions and allow the use of firmer foams to get “softer” results. The compression modulus of a thicker layer could still prevent the heavier person from sinking down too far. This is all part of the “art and science” of mattress design.
If you want to swap sides with a split layering all you’d have to do is rotate the mattress 180% and you would still be sleeping on the same layering on the other side.
The choice of pillow material and design is mostly a preference choice and each person may have a different material preference in a pillow. Latex is more “springy” and some people like this and some don’t. Shredded latex can also be 'scrunched" so it can be useful for those who like the “feel” of a latex pillow but sleep in multiple sleeping positions where the pillow height or shape needs to be adjusted when they change positions. There’s more about pillows and what each person may “need” and the many different preferences that are involved in a pillow choice in the pillow thread here. While there are certainly some common “needs” with pillows related to sleeping position and body type to keep your head and neck in good alignment in all your sleeping positions … they also involve many more “preference” and “feel” choices than even a mattress and each person has their favorite type that just “feels” the best to them…
Phoenix