I don’t really like Nassarius, they only seem to go for uneaten food, which everyone else already goes for, so that’s not super helpful. If you get enough of them they can mix up the sand for you, but so can many other things, so again, not super helpful for me.
My top snail (or snail-like) cuc is by far the tiger/fighting conch. The #1 workhorse in my tanks, those little vacuums seem to take out anything (algaes/cyanos/whatever) they can reach all day everyday. They constantly move and dig into the sand for you and their size makes them a noticeable tank mate that you can follow and keep track of easier, like a fish/coral, rather than just being another one of many random snails. They even climb glass and rocks sometimes, which can be pretty cool (and funny) to watch, but they’ll primarily just keep your sandbed/BB and connected aquascape pristine.