What style of speakers to use now for Atmos?

I’m more of an audio guy but I do have a 5.1 setup and currently using rear surrounds that are a bi-pole/di-pole type speaker.
Since all this Atmos channel is here are my rear surround speakers still used as I already have or is is just some small speaker since they are dedicated channels?

Should I find some smaller speaker and use in their place that just don’t cost much or what?

In wall or ceiling speakers better since they can be hidden a little seems kind of crazy to have all kinds of little speaker boxes all around room. 
I'm at this juncture also. My understanding is that the ceiling mounting is the best option sound and aesthetically. Plenty of speakers suitable for ceiling mount but someone else may be able to recommend their specific choice.