My Platies love cambomba plants and Vallisneria, quite heavily planted in one end of the tank. I would say they would like the Amazon Sword, a nice place to rest at night, my Platies seem to like to rest among the plants when the lights go out. The male also likes to hide in the Anubias plant sometimes, a plant I would recomend.
If you ever want fry you will need something like Cambomba or fern for them to hide in, gives them more of a chance untill you find them. If your not too fussed, I've heard that fry can be a pretty nutritious dish for a hungry Platy.
My Platies absolutely love live brine shrimp. I feed them it once a week and watching them chase them is quite amusing. They also like Blood worms, and its quite funny watching them try to eat them, mostly they cant fit them into their mouths hole. I stopped using them though, last time I did I had four mosquittos flying about a few days later!
I think for Platies salt will keep any parasites at bay (Ick, fungus, flukes etc) but it is not needed, just keep the water quality very high, will bring out the colours of the fish too!