Hi mugtastic,
Any latex topper in any firmness level would be more resilient (springy) than a memory foam topper (memory foam has little to no resilience at all). There is more about the differences between memory foam and latex in post #2 here but they are very different materials that are more of an apples to oranges comparison.
A topper is primarily for comfort and pressure relief not for “support”. 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 or “sleeping system” in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel”.
It’s very unlikely that even a soft topper would fully compress or “bottom out” if you are using it on top of a mattress vs using it on a solid floor (where the only compression would come from the topper instead of both the topper and the mattress underneath it) although with a thinner/softer topper you may feel more of the firmness of the mattress underneath it and the transition from a softer layer to a firmer layer than you would with a thicker or firmer topper.
I don’t have enough information about either you or the mattress you would be using it on or enough reference points based on your experience to be able to make any guesses or suggestions about firmness but the topper guidelines I linked in my last reply have some general guidelines you can use for both thickness and firmness which along with a more detailed conversation with Sleep on Latex will be your most reliable source of guidance.
Phoenix