Technically you could use in ceiling speakers. These will however not do Atmos, only surround, so the only Atmos you'll get would be from the Arc soundbar. The only Sonos rear speakers that do Atmos are the Era 300's.
Even surround speakers should be placed on ear height, so I'd personally not use in ceilings.
Atmos, with either up-firing or down-firing speakers for the height channels, requires you to limit the height you set you side and rear surround channels to ensure decent separation from the 5.1/7.1 ‘bed’ layer and the overhead immersive layer.
With such a large TV you are going to have to compromise placement of the Soundbar or have the TV set higher than is ideal for most seating arrangements.
And, not to mention (oh, wait, I am) Sonos doesn’t support Atmos ‘side’ channels.