Sonos limits are 32 devices in a single Sonos Household, in ‘ideal’ network conditions then all should play fine, but not everyone’s network is in excellent shape.

With Airplay there used to be an unwritten limit of 6 devices only, but this was before Airplay2 came along. The answer is that it probably varies by the bandwidth available across the network and in my own case I tend to play my own devices mostly in three physical rooms downstairs and three rooms upstairs, so no more than 6 rooms, but that may include 20+ speakers. Playing one stream only via Airplay2 and grouping the speakers via the Sonos App seems to work best.

Note when using Wireless connections you also do not want people wandering around the place as that can sometimes interfere with the signal, as can devices like baby monitors microwaves, zigbee, Bluetooth and/or streaming 4K video across the same LAN.

My own suggestion would be to try things in your own network environment and see how far you get before any audio dropouts occur and then take a step back from that.
 

What I tend to do is use AirPlay 2 to connect to a single Sonos speaker, and use the Sonos software to then ‘group’ that single speaker with any number of Sonos speakers. I find the bandwidth necessary to use AirPlay 2 to send to multiple speakers, rather than just one, to be overwhelming, in particular to my iPhone or iPad. Since it’s a habit now, I have never tried to send to multiple AirPlay 2 targets using the Apple TV or a Mac. 
 

I have never been able to send anything beyond stereo via AirPlay 2. What I do sometimes is to send video to my AppleTV, which then sends the video and Audio to my TV set, which passes the audio via HDMI ARC to my Sonos Arc. Easier that way.