Having collected some syslog entries and gone through them, I established that I do not need remote syslog for my router and disabled the remote syslog target. But do I have to let the 2x services in subject to continue to run, or can I shut them down w/o disrupting anything in OpnSense?
Local logging uses the same services.
Applications log to syslog, syslog writes to files ...
It's a pity that they are required anyway. This is a sub-optimal solution for embedded if a service is required to run even for local logging to in-memory /var.
It's how Unix works. There is a central syslog API that has to be implemented *somehow*.