Best way to minimise CPU impact of Duplicati (macOS)?

I’m setting up Duplicati as a main backup. My first backup (I will be creating a few that will run scheduled) is for 15GB (system data) and while it is backing this up to B2, CPU is at 100% (and will remain so for a few hours). Then there will be one of several hundreds of GB (user data).

I’ve looked at the manual to see if I could find something to minimise the impact of Duplicati on the OS. I saw something called --thread-priority but the only value given is ‘normal’. What should I do to throttle Duplicati’s resource usage, especially CPU?

Better help text is available from Commandline but is a bit easier to ask for from an actual CLI. More info:

C:\Program Files\Duplicati 2>Duplicati.CommandLine.exe help thread-priority
  --thread-priority (Enumeration): Thread priority
    Selects another thread priority for the process. Use this to set Duplicati
    to be more or less CPU intensive.
    * values: highest, high, abovenormal, normal, belownormal, low, lowest,
    idle
    * default value: normal

C:\Program Files\Duplicati 2>Duplicati.CommandLine.exe help use-background-io-priority
  --use-background-io-priority (Boolean): Sets the process to use low IO
    priority
    This option instructions the operating system to set the current process
    to use the lowest IO priority level, which can make operations run slower
    but will interfere less with other operations running at the same time
    * default value: false

C:\Program Files\Duplicati 2>

however beyond above I can’t really say what’s “best way”, especially on macOS which I don’t have at all.