Hi golson22m,
OK … I understand … I thought you were looking for an adjustable bed not a mattress instead of the other way around.
ILD is a comfort spec not a quality spec and the layering and softness/firmness of a mattress depends on which design best matches his specific needs and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). What is “best” will vary with each person. There are links to some of the “theory” in mattress firmness/comfort levels in post #2 here but in general it’s best to choose based on careful and objective personal testing if he is looking locally or based on more detailed discussions with a manufacturer or retailer (hopefully in combination with some local testing) if he is looking online.
If he follows the steps and guidelines in post #1 here then he is much more likely to make the best possible choices with a latex mattress or any other type of mattress he prefers. Latex is very flexible and works well on an adjustable bed in almost any design or layering.
Phoenix