https://www.cnet.com/news/ios-11-4-arrives-with-airplay-2-messages-icloud-ahead-of-wwdc/

AirPlay 2 is all about multiroom audio, and it also brings stereo dual-HomePod music playback to HomePods. AirPlay 2 will also work on Apple TV, and can be controlled with iPhones and iPads.

But another key feature in iOS is the long-expected addition of Messages in iCloud, which syncs across all devices and deletes iMessages across everything, so you won't get quite as spammed. It also backs up iMessages so that any new device in the account can get old iMessages without restoring a backup.