Per the PL upgrades the Duelund CAST coupling caps and I believe the VHAudio caps on bias board OP in that thread are A+ choices. These will provide the qualities you seek. By the way, the PL was part of my amp rotation along with Auralic Vega dac when I was playing with various Mac mini streamers, I could appreciate the difference with streaming mods with that setup.
With Roon the Core streamer is far more important than the Endpoint streamer, Core does all the heavy lifting, this has to manage the interface, indexing of sometimes huge libraries, interface with Qobuz, Tidal or some other stream provider, and it runs the actual Roon player. All this requires relatively high level of cpu, RAM compared to more basic/proprietary music player apps, so more powerful cpu, more RAM required for a quality Roon streamer. And then we have critical need of quality lps for thee streamer, this probably the most important aspect of any streamer. Running Roon core on a stock mini isn't much better than using any other general service computer, I know because I directly compared time and again, and I did many mods over many years with a number of minis. The highest possible mini I could possibly assemble didn't come close to competing with my present custom build streamer. I can decipher the design of these off the shelf streamers, the Lumin and Antipodes spoken of here will deem any mini, even fully modified, obsolete. Now, if your'e comparing $2-3K streamers to modded mini, the modded mini can compete, perhaps win here, but then you're likely $2-3K in on modded mini.