Andrew O’Hara, Apple Insider, does an excellent job walking through AirPlay 2.

A few nuggets:

There is now a substantially bigger streaming buffer. This helps reduce interruptions due to network issues. In our testing, this was very noticeable. Audio drops were down significantly from the original AirPlay.

And:

There is now tighter sync between devices, which reduces the lag quite a bit in most situations, and lends itself to multi-room audio. There can still be a bit of lag when starting/stopping a stream, but it is definitely less than in the past.

And:

Apple TV is also AirPlay 2 ready now, so during any playing video a swipe down from the top brings down the info bar. Swiping to Audio shows any AirPlay 2 speakers that can be streamed to. If on the home screen, a long hold of the play/pause button will also bring up the AirPlay controls.

Also worth checking out is Apple’s updated list of AirPlay 2 compatible speakers, found on Apple’s Home Accessories page (tap Speakers).