I've had ramshorn snails ever since I started keeping plants, and they've never overrun a tank for me, so they must self-regulate either through food or breeding...or something. ;)
I'll find some dead shells every now and again, just remove those and you're good to go. :)
They're great for algae and cleanup, and after an experience of a tank without any snails...I won't do a planted tank without them anymore! :) They're an important piece of the ecosystem you're creating. :)
As for the albino, they do come in pinks, but for some reason mine never seem to live very long. I find the pink shells far more often than I do brown ones. No idea why.
Pond snails are tiny, they won't ever get very big. Ramshorns on the other hand are much larger, and they have a circular/spiral shell. They'll get to be about a half inch. The picture that you've shown looks like a ramshorn.
You can get aquarium root tabs, or you can use regular plant fertz sticks like for houseplants, just break off little pieces and stick them deep into the gravel. Peachii realized this some time back and has had no trouble. :) (Also, much, much cheaper, always a plus!) :)