@decooney Since using Amazon HD, have you by chance gone back and compared "sound quality", and sound stage depth with something like Tidal Connect? I have not, yet. I’m listening for any degradation with AirPlay2.
It has been a few years since I have looked at this so I gladly stand corrected if any of the below information is wrong.
In short the Airplay protocol transcodes all audio to 16/44.1 ALAC. So trying to play a file at a higher bit rate than that is useless if quality is a concern.
I would avoid using Airplay or Airplay2 at all unless the source file is encoded in 16/44.1 ALAC to begin with or you are not overly concerned about quality loss.
I have been a long time user of the original Airport Express 1st gen and also the 2nd gen as well. I have these hooked up for my garage, kitchen, and basement stereo. My family and most friends have iPhones so the convenience factor outweighs any quality degradation. In my mind this is still one the best wireless audio solutions available even though it does have limitations.
When using optical out and a good DAC it is very hard to beat the combined value of audio quality and convenience that Airplay on an Airport Express provides. However, if you do not need the convenience of wireless audio then a wired connection is ALWAYS better when playing High Res tracks!
I will say that the way the 2nd gen Airport Express handles the transcoding of High Res FLAC files is beyond horrible. I have noticed a lot of distortion on the 2nd Gen, even when using optical out. When playing the same tracks using optical out on 1st Gen Airport Express, the distortion is not noticeable unless you are using higher quality equipment, and then you should not be using Airplay in the first place JMHO...
But alas the 1gen Airport express does not support multi-room audio and is now a bit of a pain to configure so keep this in mind when purchasing. They can be had for as low as $10 off eBay though.
Since most Tidal files are 16/44.1 FLAC I doubt you will notice any audio quality issues when using Airplay. It was when I was playing 24/192 FLAC off of Amazon HD over Airplay2 that things started sounding really bad.
When it comes to how Tidal Connect functions, or how various AVR's handle Airplay2 I honestly do not know. I have had a Denon AVR-X3700H for a month now but have simply not had the time to see how Airplay2 or any wireless functionality works on it. I would still assume that all Airplay Audio is transcoded to 16/44.1 ALAC and so would avoid using it for High Res FLAC playback.
To me Airplay does have its place and still beats bluetooth when it comes to sound quality. But in short, whenever trying to get the best listening experience possible I would avoid using any form of a wireless audio connections.