That’s a tough one.  Not a fan of true open architecture.  You will not likely want to switch the 300s from stereo music listening to surround duties then back to stereo listening.  There is no easy way to do that.  
 

 If your intention is to sit in a sweet spot, close your eyes and listen seriously then the 5s in stereo would be the way to go.  It doesn’t sound like that’s your intent so the 300s more diffuse sound would work better.  Yes, grouping might be better for that less specific listening environment, but the SQ gains from getting the right channel stuff out of the left speaker and visa versa should be taken into consideration.
 

 After you figure out the best placement through experimentation just set the 300s up as surround speakers and play music through that surround system.  
 
 That is how I use mine.  Dolby Atmos music is awesome played through a surround system consisting of the Arc - Sub - 300s.  I know there aren’t that many releases in Dolby Atmos, but the library is growing.  You, of course, need to subscribe to either Apple Music or Amazon Music Unlimited to get Dolby Atmos music.

Hey! Thanks for replying MoPac. 

Yeah, my intention is majorly more diffused sound than directional. As well as the bluetooth connectivity of the era 300 is a huge plus, specially when hosting other people. 

I am not sure if the surround system would utilise the era 300’s enough for music. I have another separate TV room, where I might go for an arc or beam gen 2, I was hoping Ill keep the sub there most of the times, and move it to the entertaining space only when I have people over.

Exactly how difficult is it to move speakers from different rooms in the app? because buying everything dedicated to separate rooms will really add up my cost. My plan was to buy a soundbar for the TV room, and keep shifting the sub and era 300’s if and when required. the max I might go would be to buy era 100’s as surrounds to keep the era 300’s fixed, but even then Ill have to shift the sub once in a while. not sure if the era 300 pair alone would fill the sound up, specially when Ill have people.

 Moving the Sub from one Sonos room to another Sonos room would not be seamless.  You would have to execute the Remove Sub function in the Sonos app then the Connect a Sub function for the other Sonos room.  Not sure how long that takes and not sure if that would introduce connection problems I keep reading about in this community.  The same process would need to be done for the surrounds.

 Keep in mind if the 300s are bonded as surround speakers Bluetooth is disabled.

 The 100s would work well in a smaller room.

 Look into the “coming soon” Arc Ultra.  Sounds like maybe a sub is not even needed; just a rumor.  If you’re doing surround in both the Entertaining Area & Living Area the Arc Ultra might work in the Living Area.

wouldn’t the era 300’s be enough to cover the whole L shaped space?

 In my case yes.  I’m not much of a “head banger” so I have never really pushed any of my audio speakers that hard.  If you like it loud the 300s might do just fine.

 My surround room Arc-Sub-300s can get pretty darn loud.  I listen to a lot of orchestral music in Dolby Atmos.  The dynamic range is off the charts.  I can be listening to a piece that begins very calm and quiet then BAM!  It knocks your socks off.

 If you are going to put the 300s on the wall think about how high up you place them and what direction you point them.  If they are ear height and facing into the room someone at a party could be close enough to one of the speakers to get too much direct sound.  Also they obviously need to be near an outlet.  Maybe the Move 2 speakers are too small for your usage case, but the fact they are battery powered would be easier to work with.  They can’t be bonded with a sub or used as surrounds.