Hi,
I have this same issue too on a Mac Mini, on which I opened [this ticket] (Roon and RAATServer consuming over 300% and 100% CPU on Mac Mini) with lots of debug info in it before finding this thread.
To answer the questions you posted above @noris
Mac Mini 2018 3.2GHz 6‑core 8th‑generation Intel Core i7
Mac OS Mojave 10.14.6
32Gb RAM 2666MHz DDR4
256GB SSD storage
Its consistent for hours no matter what you do in the app.
Yes it does
Ubiquity -
185Mbps DL via Comcast DOCSIS 3 connected to
Unifi Security Gateway In turn to
Unifi 16 port managed switch
1Gbps connections on wired Ethernet to the core and library
Library is on a 6 disk Netgear ReadyNAS with dual bonded 1Gbps to the Unifi switch