Sonos / A31 Linkplay & audio signal delay

I am not a Sonos user, so I don't have experience with the Sonos products.
But I do have experience with building DIY audio streaming systems, mainly with Linkplay A31 based modules.

With these A31 modules I experience close to 2 seconds delay in audio streaming. I have been explained that this happens when 2 modules are grouped (for instance to create a stereo set of 2 speakers, this is what I mostly do). And that delay happens for reasons of buffering and synchronization.

This makes me wonder ...
  1. How does Sonos handle / prevent delay when 2 or more Sonos speakers are grouped?
  2. What module do they use instead of Linkplay A31?
  3. What modules are available in the DIY market that do not suffer from delay in audio signal when grouped?

Hope to hear from you!