Using a mattress topper on different types of mattress

I'm thinking of buying a (latex) mattress topper but have never used a topper before. But I'm not sure how it would work / feel different with different types of mattress:For example, on a tufted pocket spring mattress, would the topper sink into the tufts and so give a slightly undulating top layer or would it smooth out the feel of the mattress into a flat layer? Conversely, suppose I used the latex topper on a flat topped (e.g. memory foam) mattress; to what extent would it contribute to not retaining heat like memory foam does?