I have Sonos Play 3 and Pla 5 1st gen.
There is audio delay as much as 2 sec or more while playing youtube video with the 3.5 mm audio jack plugged on rear panel of the Sonos Play 5. No wifi used for Audio. When same audio jack is removed from Sonos and plugged into my other simple speaker, there is no delay. So we cannot use these Sonos units for watching video, but only for audio.