Yikes. Ok, so anyway, wired connections from iOS or Android phones will be limited to 24/48 with a wired connection UNLESS a DAC is in between the phone and audio output device. Now, the Chromecast protocol supports 24/96 and it can be sent over Wi-Fi to a Chromecast Audio. This doesn't help 24/192 folk as Chromecast is limited to 24/96, but I digress. The optical connection to the receiver should be sending 24/96 if it is being sent to the Chromecast Audio in the first place.
There is no need for another DAC here unless a wired DAC is connected to the phone and then a cable from it to the receiver's analog inputs is used to cut the ChromeCast Audio out of the mix altogether. Again, if we are talking Tidal MQA, then there will be no support for it over Chromecast and an external DAC supporting MQA will need to be connected to the phone for output. Wether any of this makes an audible difference really doesn't matter when one is simply trying to get what has been downloaded or is being streamed from their phone to their audio output device without conversion.
As far as Atmos, Qobuz actually has actually partnered with THX for their own brand of "Spatial Audio" presentation. It is THX Spatial Audio. You, know, cuz' we needed one more format out there. While I enjoy Dolby Atmos Music over an AVR with multiple speakers, I hate "Spatial Audio" of any flavor over headphones. But, to each their own.
Like so many video service apps and their different output specs per device used, different music streaming services will support certain protocols and devices differently as well. Chromecast supports 24/96 but that doesn't mean every service will support their music being sent over ChromeCast at 24/96. It's all so ridiculous anymore. I believe Qobuz works at 24/96 over Chromecast while Amazon Music and Apple Music do not support hi-res over Chromecast. Apple Music will go over as lossy AAC as Chromecast does not support ALAC. These things change by the minute and there are work arounds but I believe those are the basics and I am agreeable to being corrected for any errors.
Lots of capable hardware out there that are all being limited in one way or another based on different ecosystems, streaming services, protocols and licensing deals. If the music sounds good, don't dig too deep and ruin it all by stressing over the numbers. If you live and die by the numbers, well, do your homework before making any purchases and best of luck to you.