Hi davetatronic,
I really don’t have enough information about either your body type, sleeping positions, or the specific symptoms you are experiencing and whether they relate to alignment issues, pressure relief issues, or “feel” issues to make any specific comments that would be meaningful. Perceptions of softness and firmness are also very subjective and can vary widely for different people on the same combination of materials or on the same mattress.
All of the suggestions you are considering can be effective but they can all take different pathways to a similar goal. The goal is always to have a combination of layers that provides you with good PPP (Posture and alignment, Pressure relief, and Personal preferences). I would also consider these in the same order of importance (alignment being more important than pressure relief which in turn is more important than the preferences of “feel”).
Every layer and component in a mattress affects the feel and performance of every other layer to different degrees so a firmer base layer may need different layers on top to achieve a similar outcome as a softer base layer with a different combination of layers on top. As jefmoody mentioned there are so many variables and unknowns involved that there is no “formula” or “science” that can be used to make specific suggestions for someone else with any certainty. There is more about some of the “theory” involved in different types of layering and design in the links in mattress firmness/comfort levels in post #2 here that may be helpful in terms of understanding some of the ideas and concepts involved but these are only generic and not specific to any person and in the end your own experiences are the only reliable way to know which layering works best for you and it may involve some trial and error.
If you can provide a little more information about your body type, sleeping positions, and the specific symptoms you are experiencing (such as numbness or tingling or back pain etc) and the areas of your body you are experiencing them I may also be able to make a few more comments.
Phoenix