if you have a mystery snail post a pic and we can ID it.
some are tropical, some are coldwater, some are best in salt or brackish water, some breed prolifically, some don't breed in freshwater at all, some eat plants, some don't! some grow very big, some stay tiny. entirely depends on species!
One of my favorites is my ramshorn snail. I think its deliberate movement makes a nice contrast to the racing speed of the fish.
So far it hasn't reproduced but I understand it may have to do to fact my tank isn't over-fed. Every once in a while I give it a piece of zucchini or lettuce to munch.