The Sonos App currently has no AirPlay server streaming capability itself and I have not seen anything yet to suggest that may change in the near future. If you can find an iOS App that streams your audio source, like the iOS Tunein Radio App, for example, then yes you can stream the audio to different AirPlay2 devices at the same time, like a Sonos One and a HomePod. The different devices should play in sync, though I have seen reports there were some sync issues in the early release implementations, but hopefully that matter is/has been resolved.
I don’t presently have access to multiple speaker devices to test this feature, but I’m sure others here in the community may be able to comment on the sync issues following the release of the new iOS 12.0 update.