Hi amd20x6,
I think you are exactly on track and are making choices between good and good. Once you have eliminated all the worst options (which you have) then your final choices will really be dependent on your own personal value equation which nobody else can decide for you.
One part of this would be to decide on your confidence level that you are making the best possible choice in terms of PPP (Pressure relief, Posture and alignment, and Personal preferences) and ask yourself what your options would be if for some reason you make the wrong comfort choice. The ability to exchange a layer (or a topper) may be an important part of “value” for you and would be well worth considering as part of the “value” of your purchase. You can see more of my thoughts about making final choices between “good and good” that are along a similar line (but between different options) in post #2 here.
Overall … from a quality and value perspective … I don’t think that you could go wrong with any of your options and you are certainly have better choices than the vast majority of people who buy lower quality/value mattresses from major brands and chain stores.
I’m looking forward to finding out what you end up deciding 
Phoenix