Since your smart TV only has optical audio output, that's what you'll have to use if you want to use your smart TV app for streaming video. Unfortunately this does mean you will be limited to the audio codecs that will go out over optical, which is probably 5.1 discrete LPCM, or Dolby Digital and Dolby Digital Plus. If that is what gets delivered to your TV by the streaming services. Dolby Atmos will not go out over the optical connection.
If you want Dolby Atmos, you will need to get a separate streaming box and use that instead of your TV's built in apps.