I really like water sprite but no shops here seem to carry it.
I had a 10gal, as a teen, that was full of plants and I would occasionally take about half of what I had to a store and get some store credit for it. It does grow very fast.
The two types are actually the same plant. The leaves shape acording to wether they are floating or planted. the floating ones will develope the broad leaves and the planted ones will develope more feathery leaves. It does not mater which you actually plant, they will just change as they grow.