You could connect to the speakers via AirPlay from the Apple TV.

Perfect, thank you.

By connecting 2 Era 300 to the Apple TV 4K can I get Dolby Atmos?

Thanks 

Certainly not. You need a soundbar that does Atmos, then pair the Eras to that.

Airplay is a stereo-only transport.

But... Apple tv 4k + 2x homepod 2 gets Dolby Atmos.. 

That kind of setup doesn‘t use Airplay… it’s a direct stream that comes to the home pods. Apple TV just initiates that as a remote.  
Also it’s limited to Atmos music using Apple music.

It should also work with tidal atmos albums. I only have a 2nd gen homepod and I'm considering whether to get a second one or look at something else like the Sonos Era 300. But if I also have to get the Arc soundbar the range of alternatives widens.