I have 2 x Play 1, Playbar and Subwoofer in use. Because of Airplay 2, I then bought another Sonos ONE. It's enough if one of your Sonos components is Airplay 2-compatible, this then transmits the signal to the other speakers. Of course, you can then only control the one Airplay-enabled device from your iOS device - but you can then control the other devices via the Sonos app.