Hi Turtlebed,
When it comes to questions about PPP … there really aren’t any “theoretical” suggestions about layering that I can give you that could be more useful than your own careful and objective testing on each combination.
If your testing is a good approximation of your own sleeping experience then based on your feedback it seems to me like option A was the best “match” for you and it would certainly be “in the range” that would be suitable for your body type and sleeping positions “on average”. Some people may even consider it to be too firm … especially with Dunlop latex … but each person can be very different in their specific needs and preferences. This combination would also give you the option to put the 2" soft layer under the 3" medium layer which would give you a firmer sleeping surface (but softer than option D).
If you were to choose a different combination such as the option D you were considering then you would be introducing more uncertainty and risk by buying a mattress and then adding a topper where you can’t test the combination in person and I wouldn’t normally suggest buying a mattress with the intention of adding a topper afterwards (see post #2 here). If you do decide to go in this direction anyway then I would sleep on the mattress first and then use the information in post #2 here and the topper guidelines it links to as a reference point to choose a topper that has the best chance of success but making a “blind purchase” is always more risky than buying something that you have tested in person.
Phoenix