There are dozens of species of freshwater snail, and some have issues while others do not. If you have live plants, you want to avoid any snail species that is likely to eat plants; some do, many do not. Aside from the plant issue, snails are very helpful in any aquarium. They eat all dead organics, which includes fish poop, dead plant leaves, uneaten food. This is a benefit because it breaks the organic matter down faster so the various bacteria can better handle it, and quicker.
I have always had one or more of the very small "common" snails that frequently arrive on plants. Pond snails, bladder snails, ramshorn snails and Malaysian Livebearing Snails are the four most common. None of these eat healthy plants (though the ramshorn has been accused of this by some), they get everywhere you cannot, and they are a benefit. They will multiply according to the available food, but you never have to add food just for these snails, they are scavengers in a sense.
There are larger snails, some will eat plants, some do contribute to the bioload, most (there are a couple exceptions) will reproduce readily according to the food.