How safely TEST move to new system

The guide is indeed referring to moving an entire setup – not cloning it.
https://support.plex.tv/articles/201370363-move-an-install-to-another-system/

That being said… cloning might not be necessary if you’re ok to keep the original server shut down while you’re testing the new one.

Alternatively… there’s a guide in the Linux Tips & Tricks section that details how to handle copying a server (vs. just moving it):