Unless there is a feature on your TV that allows audio to be played out of the TV speakers and external speakers at the same time, the audio will only play out of the ceiling speakers. Streaming music from the Sonos app will also only play out of the ceiling speakers.

Would you recommend getting the ceiling speakers at all then or just stick with a soundbar? And will it be the same story with that? Sorry for my lack of knowledge, not a clue 

In-ceiling speakers are usually not recommended for a home theater setup especially for the front channel speakers. Speakers should be placed at or near ear level (except for height channel speakers). I would go with an Arc or Beam (Gen 2) and consider adding a Sub and One SLs as surrounds.

And, yes, the audio will only still play out of the external speakers.