I know that "off the beaten track" means "unusual". Can it be used before a noun and after a verb?
- an off the beaten track place
- This holiday is off the beaten track.
Is it used only when talking about things?
Yes, you can.
"Off the beaten track" means out of the ordinary or unusual, but that's not its only meaning. It can also mean in a remote location, or somewhere that's out of the way or out of a central, popular or touristy area.
You can use it as an attributive adjective:
Like what @J.R. commented, you'll need hyphens to make an adjective out of a phrase.
You can also use it as a predicative adjective:
It's often used for things and places, but it can also be used to talk about people: