Update: Everything seem to be running rather well with the database on the RaspberryPi4, the database & RadioDJ are amazingly fast and sleek.
Apart from a Raspbian/Linux update screwing things up last week, everything is working as anticipated (good job we had a copy of the disc image backed up)
We're currently running a DHCP server., MariaDB, PiHole and our home web server from it.
The Pi rarely runs over 56*c so it doesn't run that hot.
So in short I think the RaspberryPi4 is one of our better purchases this year.