Hello fermata,
I don't have first-hand experience with it, nor feedback from other users so far that I recall. I understand that there was (and perhaps still is) an issue whereby Macs containing Apple's T2 chip (as the 16-inch MacBook Pro does) had issues with occasional audio glitches with audio interfaces attached via USB. Hence it might be best to use an audio interface connected via Thunderbolt instead (e.g. RME and MOTU make some).
In terms of hardware specification, it should be excellent for running for Hauptwerk. (I would go for the 2.4 GHz 8-core i9 CPU and 64 GB of RAM options, with at least 1 TB of storage.)
Any new Mac will ship with macOS 10.15 ('Catalina'). Hauptwerk v4 wasn't compatible with macOS 10.15 and couldn't be installed on it -- I definitely wouldn't recommend trying that. v5 installs properly on 10.15 and is supported on it, although there are still a couple of minor (mainly cosmetic) compatibility issues with it, to be resolved in a future version. In general v5 should be fine to use on macOS 10.15.