3. I would add serenading each other. If they really start yowling, it's not long till it's growling and hissing. Serenading seems to go merrily on and on. I don't think they do meow to each other except as kittens. Maybe momma cat does to the kittens, but I don't know.

4. I think one cat per home is plenty. Certainly it's hard enough to type with one cat in my lap.