Hi Demeter,
Welcome to the Mattress Forum!:)!
Congrats on the St Dormier pad!
Yes, generally the issue of the sleeping microclimate on a mattress is a complex one. Heat and the inability to reposition, both tend to be characteristics of memory foam, especially when compared to previously sleeping on an innerspring mattress. Generally, Innerspring mattresses, do a good job of sleeping cool since they have less foam to trap heat in the mattress, but even so, some innerspring mattresses still end up sleeping hot depending on the very top layer of foam.
I am glad that you are enjoying new pad mattress combo and that it is just right, for you to still feel the softness of the mattress, You are correct that layers that are closer to the top sleeping surface will have the greatest impact upon comfort and sleeping temperature (including your mattress pad, sheets, and linen). There is more about the many variables that can affect the sleeping temperature of a mattress or sleeping system in post #2 here.
Thank you for mentioning the pillow sleep tips for side sleepers for any other consumer members that are reading your post. Pillows are a very personal choice and different people will have very different pillow preferences or different opinions about what they perceive as firm and soft or the general type of pillow that “feels” good to them but some of the information in the pillow thread here and the posts it links to can help you choose a pillow that is the best “match” for you and the mattress you are sleeping on.
Thank you again, and let us know how it works out in the long term!
Phoenix