Hi gu-obos,
Your process is a little different from the norm. The safest way to choose a mattress would normally be to test the exact mattress that works best for you or to test a mattress / topper combination that you plan to purchase or in some cases to add a topper after a mattress purchase if you end up making a choice that needs a little more softness than you thought when you were testing the mattress. It’s not nearly as common to buy a topper first and then try to match a mattress to the topper. I would think that there are enough mattresses that use comfort layers that are already in the thickness and firmness range that you prefer that this approach generally isn’t necessary.
If you do plan to take this approach though then I would just choose a topper that your research seems to indicate that you may like (based on the top layers of the mattresses you test) and then test mattress topper combinations until you find the mattress that works best with the topper you chose.
You may also want to consider testing some mattresses that use Dunlop which isn’t as “springy” as Talalay latex so you can decide if this would be a suitable choice for you.
I would tend to agree with this although it’s not so much that a natural fiber topper won’t last as long but that it will compress and become firmer as it packs down so the “feel” of a natural fiber topper won’t last as long as high quality foam even if the topper itself isn’t worn out. This will also depend to some degree on how the natural fiber topper is made.
In general terms memory foam tend to be warmer than other foam types but there are also other factors that combine together that can also affect the sleeping temperature of a mattress that can make a difference as much as the foam (see post #2 here). Gel memory foams may also be a little cooler than some memory foams. You can read more about gel memory foams and their effect on temperature in post #8 here and the posts it links to. The effect of the gel will depend on the type and amount of the gel that is added and this may not be possible to find out exactly so you would be dependent on the knowledge and experience of the manufacturer to tell you how their specific memory foams may compare to others in terms of sleeping temperature.
There are some other options available in the Boston area in the link I posted earlier that may give you the chance to test some different options and materials as well.
You may be making this more complex than it needs to be and you are almost in the realm of designing your own mattress. I would tend to keep things much more simple than considering combinations of mattresses and toppers where there is no way to predict how they will feel for you outside of your own experience.
In some cases yes but I think a cover is a good idea to protect the topper material from damage and/or oxidation.
Phoenix