Also of note is peer-to-peer AirPlay, let’s unpack that a bit.
Let’s start here:
Use AirPlay to wirelessly stream content from your iPhone, iPad, or iPod touch
https://support.apple.com/en-us/HT204289
Where it says "You can stream content to your Apple TV (3rd generation rev A, model A1469 or later).”
Check this out to determine model:
Identify your Apple TV model
https://support.apple.com/en-us/HT200008
So, 3rd gen Apple TV model A1469 and the current 4th gen Apple TV will both do peer-to-peer AirPlay. Apple TV 4th gen runs TVOS, which is the future of Apple TV, and previous models do not support TVOS.
If it were me, I’d wan’t to standardize on 4th gens for new purchases, and ideally I’d want to weed out anything less than a A1469 3rd gen in my fleet.
Does that help?