This is how I play HD music on my iPad Pro 13 inch.
I have an HD iTunes library set Up separately on my MacBook Pro. I open it with home sharing on. The iPad sees and it just plays the tunes through the headphone jack BUT downsample to CD.
The simple solution I'd to get an external DAC and Headphone amp that doesn't need external power. Dragonfly red, latest version will work this way. If the DAC/amp needs external power a powered hub will work but the new USB 3 lightning camera connector is easier. It has a power cable connection so hook up the charging cable to. Audioquest had an article to show the hookup but I've seen on other sites also. The music will be HD to the DAC so there is no downsampling.
But to be portable you need to load your HD music into a third party app, from the App Store. Onkyo and TEAC have an HD player. BUY ONLY ONE: THEY ARE THE SAME APP! Any third party app needs to be connected to an external DAC that plays HD. Onkyo/TEAC will play DSD if the connected DAC will handle it. Try VOX from the App Store also.
Can you play to a desktop DAC and then into your HiFi? Yeah. I connect the USB port from TEAC UD-301 to my iPad and play DSD with the TEAC or Onkyo apps. I have both.
What about a wireless drive storing the HD music? Hit or miss in my testing. The wireless connection may not support the necessary bit depth, or there are syncing problems, or the media player that ships with wireless device won't play the music directly. I've tried the app "FileBrowser" to connect to my wireless Kingston but not with great success.
So far my best results have been loading the music into the HD player and using an external DAC.