Suzhou Opera Museum introduces three local performance traditions: Kunqu opera, Suqu opera, and Pingtan storytelling with ballads. The displays are most useful if you want context before seeing a live performance in Suzhou, since all three forms use the Wu language and can be hard to follow without background.
Check the performance schedule when you arrive. Even a short demonstration gives a better feel for the music, costumes, and spoken rhythms than the static exhibits alone.