Sonos offers 30-day home trial periods in most regions, so you could buy-and-try? 

hi nik9669a. Thank you for your answer. I’m aware of their trial policy. However, mounting those 300s require some electrical wiring in the atic that I don’t wanna just do all that work for a trial. 

That’s what ‘temporary’ extension cords are for. 

I am not a huge fan of overhead rear surrounds, the recommendation is for ear height, which suggests speaker stands behind the couch. But you’ll still have power concerns. As I do. 

Atmos will always be challenged by that vaulted ceiling, too. So ‘immersive’ depends on your ears. 

Atmos is actualy a big deal for me and if this setup doesn’t work with that vaulted ceiling I probable have to use in-ceiling speakers and I don’t think sonos Arc supports Atmos with in-ceiling speakers or does it?

I'd do temporary wires, temp mounts using 2x4s would work too.

A fancy multichannel AVR, 9 to 13 channel, and a lot of speakers, properly set up might be needed if you want near perfect sound.

My room is awful but I decided Sonos was good enough and skipped the AVR install, setup and most importantly family friendly daily use issues.

In ceiling speakers are likely a poor choice for Atmos sound. Dedicated surface mount ones, with multiple directional drivers should prove far superior.