Karl pretty much said it. All AQ salt is is pure NaCl, basically table salt without the anti-caking ingredients. A complete waste of money with no use in the aquarium trade IMO. It certainly has no use for plants.
I think the "livebearer salt" you can get is basically sea salt - identical to what you'd get under that name down at the Supermarket. As for the "tonic salt" - who knows? The manufacturers certainly aren't telling.
What bugs me is how some of the best respected names in the business are in on this scam - and the pH adjustment scam for that matter. AP, I'm looking at you.