I also have high pH and hard water, and my pygmy cories are thriving! They are super entertaining to watch. They are nocturnal, so don't count on them playing during the day. However, mine come out in the evenings and play in the filter stream. I love their itty bitty selves! They are ridiculously cute little fish, in my opinion. :) I have them in with neon tetras, who also are thriving. It's really more about what they are used to, as far as I can tell. Mine all came from my LFS, so they have no issues with the local water.
6 is generally the recommended minimum for pygmy cories, and supposedly they are good fish to have in with bettas.