Regular apple snails, Pomacea bridgesii
will leave the plants alone for the most parts. Some accidents might happen with snails that are hungry and don't have any other food, but they are rare occassions.
The nasty, big and mean apple snails (well, they aren't nasty or mean), Pomacea canaliculata
, will eat all your plants and then they will crawl out of the tank and try to eat your dog (well, only the first part is true, but I got carried away with my doomsday predictions
How to tell them apart? Well, the easiest way to be sure that you have P. bridgesii
is to buy a pink apple snails. That's a 100% brig, no other species has that colour variation (same goes with blue, purple, ivory and some other colours). Then if you are really interested in the subject, you can read about the differencies at The Apple Snail (Ampullariidae) Website
and really be able to tell the species apart.
Where can you get a pink apple snail or another colour variation of P. bridgesii
from? Get them from a reputable breeder, for example: The Snail Store by Rainbow Snails
But to be honest, apple snails aren't the best choice for a planted tank. But the reason isn't that they would mess up the scape, it's the water parametres. Apple snails won't look pretty if the pH is under 7, their shell will slowly dissolve away. And the females also like to climb out of the tank to lay eggs above the water level, so an open tank and apple snails isn't a good combination.