Hey Serenitystar80,
Nice to see you again! Congrats on your new topper shopping journey 
. Thanks To NikkiTMU for the excellent support and to @MrYabo for your suggestions. It appears that your interests are in a soft, non-toxic, non-dunlop latex topper option and in memory foam.
The short answer to your question is “Yes, they both could be soft and sinking in feeling”; that is the nature of memory foam. However, as only you can “feel” what you feel on a mattress, it is impossible to predict how your body would personally perceive memory foam’s feel and response as opposed to someone else.
Memory foam’s responsiveness is mostly independent of its density. However, density is directly related to durability. Foam Density is the weight per cubic foot of a foam. Good quality Memory Foam is usually over 5 lbs per cu. ft., and HR polyfoam is 2.5 lbs per cu. ft. or higher. The higher the density, the more material is used, the slower the response time is, and the longer the memory foam will last. Memory foam’s slow response naturecan make it difficult to control how far you sink into a memory foam layer, as it can soften over the course of the night and what started out as correct spinal alignment could turn into a “hammock” position and a backache by morning. You may consider using the minimum thickness that is suitable for your needs and preferences. This Phoenix postoffers more insight regarding memory foam’s unique nature and response.
Do you have access to local COVID-safe showrooms for testing memory foam toppers? If you don’t have a point of reference for its unique “hug-like” feeling, you may find mattress testing helpful for deciding whether this type topper will improve the comfort feel of your mattress. Hope this helps some and let us know which topper you decide on 
.
Sensei