Are gel-infused memory foam toppers actually cooling?

Only partially. Across r/Mattress threads, the consensus is that gel infusion slows heat buildup in the foam itself but doesn't actively cool the sleeper — hot sleepers who layer a gel topper on an all-foam mattress often still report overheating. A fiber or bamboo-viscose pillow top tends to sleep cooler than any gel foam, at the cost of less pressure relief.