Hi Pura Vida,
That’s not a dumb question at all.
There is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support/alignment” and “pressure relief” and “feel” that may be useful as well.
Generally, a heavier person will tend to sink down more “through” softer comfort layers (such as in the Beautiful), and there can be a greater potential for poor alignment in such a situation. Of course, every person is different in their levels of flexibility, strength and sensitivity. While having some sort of a straightedge can be assistive in looking at someone’s alignment, a rough eyeballing, combined with a person’s own personal impressions, are usually quite satisfactory. It’s rare that someone would have a “perfect” alignment, as we commonly think of like when we look at a skeleton. There’s always some sort of individual variation. The key would be looking for something that appears “unusual” or excessive in lateral curvature (when on the side).
Between those two models, the Beautiful certainly uses much softer material (15 ILD) in the uppermost comfort layer than the Nature (21 ILD) and the uppermost layer is thicker (3" vs. 2").
Phoenix