Java Moss doesn't "take over". I have Christmas moss and a Moss ball and neither have "taken over". Does it grow and attach? Yep. It really adds to the tank, too, and will attach to those pots.
Duckweed, on the other hand, WILL take over. Absolutely, 100%, guaranteed, will take over. Unless you want a lovely top layer of duckweed that will constantly grow and you will have to throw out, then don't buy it.
Swords do great in hard water. They don't mind a bit. I currently have a very large Melon Sword but it is browning a tad, I haven't quite figured out why, but I think from lack of nutrients. It's been striving for awhile, though.
All the types of vals will do great as long as iron supplementation and good water quality is provided. I love vals!
Java ferns will do good in most conditions. I have no idea about Najas or Water Sprites. Most plants will do okay as long as acclimated and properly adjusted to hard water.
I would adjust your tank and line the back of your tank with a couple vals, then I would attach a type of moss (whichever you prefer) to your pots, and in the front I'd place a smaller plant, maybe put down some java ferns, maybe some crypts? (I have crypt wendtii that do great in my hard water, but they do completely melt when you re-plant them, but they stay nice and low for the front part of the tank!)
You'll need WAY more hiding spaces for a sorority than you have... So pick dense plants and aquascape with them!