Hi Elisabeth,
Regarding temperature issues, there is more about the many variables that can affect the sleeping temperature of a mattress or sleeping system in post #2 here that can help you choose the types of materials and components that are most likely to keep you in a comfortable temperature range.
In very general terms … the materials, layers, and components of a sleeping system that are closer to your skin will have a bigger effect on airflow, moisture transport, and temperature regulation than materials, layers, and components that are further away from your skin and softer mattresses or foam toppers will tend to be more “insulating” and for some people can sleep warmer than firmer versions of the same material.
All foams and materials insulate to a degree, and a softer mattress that allows you to sink in more will tend to feel warmer and also allow less area to be exposed for efficient heat dissipation, versus a harder feeling mattress that doesn’t allow you to sink in quite as much. As for foams, latex (specifically Talalay) tends to be the most breathable, followed by polyfoam and then memory foam. I’m not sure for your perception of feeling warm on the Posh + Lavish mattress (maybe you didn’t like the thickness of the wool layer under their covering), but sleeping warmer on latex isn’t as common as memory foam. But of course this is quite individualized and subjective.
Phoenix