It depends entirely on the snail species ....
Some snails will eat your plants, others will take over your tank given the chance.
Some snails are beneficial, eating detritus & decaying plant matter, aerating the soil, eating algae ....
As long as the snails don't eat my live plants, I leave them alone. I would control the population by not feeding too much so there isn't too much left overs for them.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.