No. Once you “split” the system, the One SLs are no longer configured as surround speakers for the Arc. You must choose one or the other (surrounds or stereo pair) or switch back and forth between the two which would take far too long, not to mention you would lose any Trueplay tuning each time you switched.

No, not in the way that the Sonos system currently works. Each speaker, or set of speakers, are part of one specific ‘room’, and not multiple rooms. Essentially, you’d need to unset them up from their surround duty and move the to another ‘room’ each time you wanted to switch their use.

It is much easier to define their play back in the Arc’s  room settings as ‘full’ rather than ambient so they act as normal stereo speakers, and adjust the volume for music streaming only to deemphasize the Arc.

Thank you