Hi Hobotrader,
The the only real “guarantee” you have is to actually lie on the combination you are considering either in a storre or at home after the purchase. There are so many variables between people in terms of body shape, weight distribution, sensitivities, and preferences (as you know from your own experience) not to mention specific medical or physiological issues between people that what works for one may not work for another. Sometimes if you are really unsure it can be a good idea to experiment a bit with various toppers that are purchased from a big box store or other retailer that has a great return policy.
The guidelines that I would use for a topper choice though are in post #8 here.
A 2" topper would be a good “standard” choice that is a compromise between improving pressure relief and having less risk of alignment issues.
Phoenix