Hi guest01,
Based on “averages” a medium base layer would probably be OK but it will really depend on the specifics of the mattress and on the body type, weight distribution, and sleeping style of the person and the only way to know for certain would be based on your own personal sleeping experience. All the layers and components in a mattress will have some effect on the layers above and below them and on the mattress “as a whole” but the upper layers will have a bigger effect on the feel and performance of the mattress than the deeper layers of the mattress. This would be especially true for lighter weight ranges who don’t compress the deeper layers as much and in some cases may not even feel a noticeable difference between slightly firmer or softer bottom layers although it may still make some difference in alignment and how you feel when you wake up in the morning rather than how you feel on the mattress when you first go to sleep at night.
Yes it’s certainly possible because most stomach sleepers do best with a very thin pillow or in some cases no pillow at all. Stomach sleeping is the most risky of all the different sleeping positions because there is a much higher risk of the pelvis (which is the heaviest part of the body) sinking down too far and hyperextending the lower back which can certainly lead to lower back pain. This is why a firmer center zone can be helpful and a using a thin pillow under the pelvis and lower abdomen can also help with stomach sleepers as well. Stomach sleeping also has a much higher risk of neck problems because you are sleeping with your head and neck twisted on its side.
A pillow that can be “scrunched” into different thicknesses (such as shredded foams or feathers or down) or can be useful with combination sleepers so you can sleep on different pillow profiles when you change sleeping positions. A pillow in between the knees can also help with alignment for side sleepers and a pillow under the knees can also help with lower back pain and alignment for back sleepers.
A suitable pillow is an essential part of good alignment for the head and neck and upper body because the gaps between the head and the mattress and the curve of the cervical spine needs to be supported just like all other parts of the spine. Like mattresses … there are certain “needs” that depend on body type and sleeping positions but with pillows, personal preferences play a more important role because the face is much more sensitive to textures, temperature, smells, and other more subjective “feel” based properties of a pillow. There is more about choosing pillows in the pillow thread here.
It’s very common to need a different pillow when you change mattresses.
With combination sleepers a mattress that has “just enough” thickness and softness in the upper layers to relieve pressure points when you sleep on your side (but not more than you absolutely need) will generally be less risky in terms being too soft to maintain good alignment when you sleep on your back and on your stomach.
Once you have found the “best possible” layering combinations with the layers and zoning components that are available to you then you can also do some additional “fine tuning” with a mattress pad or a relatively thin topper that may help with the tossing and turning. It’s also possible to use the zoned layer on the bottom and the solid layer in the middle which would reduce the effect of the zoning but I would do some additional trial and error with the zoned layer in the middle first.
Another option that may be a good “pointer” may be to remove the top quilted cover for a few nights (again once you have done some additional trial and error) which may improve the ability of the latex to contour to your body shape and may provide some useful feedback as well. There is more about the pros and cons of a wool quilted cover vs a more stretchy knit cover in post #6 here that may be helpful.
Phoenix