So it will be AirPlay that is limiting what you can get, I believe.
At the present time, the PM7000N is only “Roon Tested” and is not “Roon Ready”. If it were Roon Ready, then Roon would be able to deliver 24-bit/192kHz streams over the network using the RAAT protocol.
It appears that there is certification being done by Roon Labs for at least some Marantz/Denon products, however it is impossible to say when this might be completed, or indeed if the certification will be successful at all. So, I wouldn’t hold your breath in the expectation that your device will become Roon Ready soon.
There is a third-party HEOS extension for Roon that has been developed by @peter_richardson, see:
This might be a solution for you, but would involve being able to run the extension alongside Roon. I’m not certain whether it can be run on MacOS and if you went to a ROCK/NUC setup, it certainly couldn’t be run on the RoonOS in that setup. Those of us using a ROCK/NUC setup (which includes myself) use an RPi4 running DietPi and the Roon Extension Manager for this.