Anything with good airflow will produce more clouds. Anything in the
doge series, MutationX v4, like you said, The Troll
rda. Really the clouds boil down to your actual build. There are so many options to choose from that have a ton of airflow, it's making sure your build produces enough vapor to make use of it. An Airek RDA with the right build will produce a ton of vapor, it's just getting the build right to make use of all 3 1/8 airholes is the trickier part.