Hi cantsleep,
Any topper can be used on memory foam but a topper will also affect how much heat can reach the memory foam and affect how it feels and performs so it will also depend on the thickness and type of topper and the heat sensitivity and response of the specific memory foam in your mattress. The most common topper for a memory foam mattress would be a softer memory foam topper but latex can also work well (again depending on the specifics of the memory foam and the firmness and thickness of the topper) and will give a more “resilient” surface feel but can maintain “some” of the slower sinking in of the memory foam underneath it. Thicker toppers can affect and “firm up” the memory foam underneath more than thinner toppers.
It’s not really possible to predict the type of topper that someone may need on a specific mattress until they’ve spent some time on it (and even then it can involve some “educated” trial and error) but the topper guidelines in post #2 here and the posts it links to are based on a self assessment of how much more pressure relief someone believes they need and may be helpful once they’ve had the chance to sleep on the mattress.
It would certainly add some extra softness and change the “feel” of the mattress and it’s more “airy” and to some degree will “flow” around the pressure points rather than just compress so it would be less risky in terms of affecting alignment and would probably affect the response of the memory foam less than a solid foam layer. Whether it’s it’s “right” for any individual person though would depend on how much extra softness they need and the specifics of the person/mattress/topper combination. It’s a great product in the right circumstances and you can see some of my comments about it in post #38 here.
Phoenix