Hi TimJohnst,
It definitely sounds like you’re on the right track and all makes good sense. If you’ve not seen it, the best place to start your research using this website is from the tutorial post. Phoenix does a wonderful job of identifying the steps to follow to help you find the best mattress for yourself.
Besides being a wonderful starting point, the tutorial helps you understand some of the ways to evaluate if a mattress has a useful/suitable amount of softness, as well as correct support, as you wrote.