Hi kate,
Both Dunlop and Talalay latex come in a wide range of firmness levels. As an example you can see the ILD ranges for the different firmness levels for Latex Green 100% natural Dunlop in post #2 here although not every manufacturer or retailer will have all the different firmnesses available.
I would also keep in mind that ILD/IFD ratings don’t compare well between different types of materials or between different types and blends of latex partly because ILD/IFD is tested differently with polyfoam than it is with latex and produces different results (see post #6 here) and partly because there are other specifications besides ILD that can affect how soft or firm a layer feels (see post #4 here).
Every layer and component in a mattress (including the cover and quilting) will affect the feel and performance of every other layer above and below it and the mattress “as a whole” so it would really depend on the body type and sleeping style of the person and the overall design of the mattress (not just a single layer).
“Support” is often misunderstood because the goal of a “supportive” mattress is to keep the spine and joints in good alignment and this requires the type of contouring support that allows some parts of the body to sink in more (softer) and some parts of the body to sink in less (firmer) and this will vary on an individual basis. 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 “comfort/pressure relief” and “feel” and how they interact together.
If you sleep on your side or are in lower weight ranges then based on “averages” you will tend to do better with softer comfort layers (or a softer topper) than someone that sleeps on their back or stomach or that is in a higher weight range. Since both of you are in a lower weight range then the odds are higher that you may do better with softer comfort layers than someone that is heavier but the only way to know for certain whether any sleeping system or combination of materials and components is a good “match” for you in terms of PPP and how well you will sleep on them will be based on your own personal experience.
Phoenix