Tips/limitations/gotchas on how Sonos enable AirPlay on older models?

We have Sonos home config with several of the older generation of devices (Play:1, Play:3, and Soundbar). We'd like to make these easier to access from our Apple devices, so am contemplating buying e.g. a Sonos ONE based on the claim that this will enable AirPlay to control all the speakers. However posts like these ~3 years definitely suggest that the exact operating functionality and compatibility was not clear:

• How will extending AirPlay work
• Access to AirPlay 2 when using One as surround speakr

Since it's been 2+ years since this was released, I'm hoping to now understand how this will works and (most importantly) any limitations or "gotchas" we should be ware of (e.g. potentially relative to speaker positioning, models, or grouping). For example:

• Will this work if I'm closest to one of the existing speakers, potentially out of range from the new Sonos ONE?
• Will it work if the speakers are part of a group? What if they are not part of a group?
• Will this work if the speakers are playing different music (e.g. can 3 different iPhones connect to 3 different speakers over AirPlay to play different music)?

My apologies if this has already been written up somewhere--please feel free to point me to a FAQ or similar.

Thanks,

Ramon