You make a good argument to not pursue a dedicated streamer. However, there are many here who were in OP position and believed what they heard sounded great until they made a switch to dedicated streamer and freely acknowledged the improvements from a dedicated streamer or server. Simply put, the proof is in the pudding.
I say this to @whitestix If you have the funds then a streamer like Aurender N200 will definitely sound better than the iMac. A well appointed system like yours especially with LaVoce DAC can greatly benefit from a dedicated streamer. And N200 allows up to two 8TB SSDs storage for your music. Let N200 will be the only source for your stored music and streaming from Tidal or Qobuz. Just keep the external HD around as your back up.
If you get a dedicated streamer like N200 then you need an iPad to navigate / browse music from Tidal and stored music. As long as both your N200 and iPad on same network, iPad is going to communicate with N200 wirelessly. N200 has its own proprietary iOS app called Conductor. I am including a link below for Conductor app so can see for yourself, the layout and functionality,
https://www.notion.so/Conductor-App-Manual-V3-a78b4ddbe61440bc988fce52e34d0dfb
I do not want to muddy the waters by mentioning ROON here as you’re still trying to process all the information. A dedicated streamer like Aurender or Lumin would be the way go given your excellent system.