Not quite what you’re looking for, but LG TVs have a feature called “enjoy TV sound together” for this exact purpose. You can output to multiple audio sources.

http://kr.eguide.lgappstv.com/manual/w22_mr2/global/Contents/settings/accessibility/simultaneousaudio_k_u_b_e_c_a_t_j/eng/w22__settings__accessibility__simultaneousaudio_k_u_b_e_c_a_t_j__eng.html

The Logitech doorbell used to have a lot of problems with overheating in warm weather and losing connection. They fixed it with a firmware update last year I think. Mine has been rock solid.

It’s use 125mpbs max for 4K Bluray. But typically between 50-80mbps. I

One reason could be that they have been mastered differently for streaming vs bluray.

The TrueHD audio is also lossless compression, while the DD+ version is compressed.

Is there a difference in sound when the file is in Dolby Digital Plus 7.1 vs. DD+ 5.1 ? vs. TrueHD 7.1?

Unfortunately the AppleTV only supports atmos when it’s in a Dolby Digital Plus 5.1 container. DD+ 7.1 or TrueHD is not supported and will be converted to multichannel PCM.

https://support.firecore.com/hc/en-us/articles/217735707-Audio-Options-tvOS-