gjournal, turn off automatic synchronization clarification

[Abner Gershon]

Man page quote:"

  When *gjournal* is configured on top of gmirror(8)
<https://www.freebsd.org/cgi/man.cgi?query=gmirror&sektion=8&apropos=0&manpath=FreeBSD+12.2-RELEASE+and+Ports>
or graid3(8) <https://www.freebsd.org/cgi/man.cgi?query=graid3&sektion=8&apropos=0&manpath=FreeBSD+12.2-RELEASE+and+Ports>
providers,
     it	also keeps them	in a consistent	state, thus automatic synchronization
     on	power failure or system	crash may be disabled on those providers."


I am planning to use 4 disks. 2 in a gmirror for data. 2 disks with
mirrored partitions for the journal.

Should I turn off gmirror auto sync for just the data provider, just
the journal provider, or for the journaled device itself?

Please provide example.

Thank you.