Hi Fabphilly.
The first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP (Posture and alignment, Pressure relief, and your Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
As a side and back sleeper, the comfort layers generally need to be a little softer and/or thicker (ranging from 2 - 4").
I would say the Oceano is only slightly more natural than the Sparrow. The Luxury Bliss is all natural (where reasonable, obviously the coils are metal) and organic. The EcoCloud also has natural comfort layers (but not organic).
I hope this helps you moving forward!
Nikki