If you can move the Arc another 1-2 feet closer to you, that could possibly help you hear the height channel effects from the Arc better.

Most people keep the Loudness setting enabled.

Experiment with the angle of the Era 300s. Try them facing the front wall straight on. Then try them angled towards you. Choose the angle that sounds the best.

Since the Era 300s are so close to you, the Surround Audio level might need to be lowered so it doesn’t overpower the audio playing from the Arc.

Play a scene or song in Dolby Atmos with clear height channel audio. Then adjust the Height Audio level so it sounds clear and matches the audio level from the other channels.

Everyone’s room setup and sound preferences are different. So adjust the EQ settings and Sub Audio level to your liking.

You might need to tilt your arc for best atmos. Have you seen Peter Pee’s video on the subject? I found it very insightful: https://youtu.be/hu8TLAco2tI?t=712 The link is timestamped to bring you to the atmos specific part, but might be worth watching the whole thing.

With regard to the Era 300s, people here have said to aim them straight towards your tv without targeting them towards you. I think that’s only effective if they’re directly behind you, otherwise your atmos channel will miss you entirely. Since it sounds like yours are closer to parallel, I would try aiming them more directly towards you and see how atmos and also importantly how rear sound effects sound. 

Thank you! I appreciate the advice!

Hello. Did you manage to create a group with all together? The sonos App does not accept it, and the TV volume and mute remote control buttons only affect the arc+sub group.

Make sure the surround speakers are separate rooms before you add them as surrounds.  They can't be stereo paired, they need to be single rooms.

Hello. After some hours of creating-deleting groups, somewhere else I found the same answer you give me. Thank you, they sound nice and synched.

I believe I added them as surrounds after I added them on my app... but I don't recall adding them in different rooms specifically... if they were added differently than what was stated above, would that change the way they sound or just not work at all. They seem to be working for me at the moment..

And one more question, the front driver's are disabled as surrounds at this time? Thanks