Does 2010 27" led cinema display need usb for the monitor to work?
Of course, needed for usb connections on the display if you want to use them.
But if you just plugged in the mini display port would the monitor work ok?
Mac mini (2018)
Correct.
Cinema Display's USB supports these: 3 USB ports/Sound and camera.
If you only want the screen portion to work - mini display port will do just it.
Best