I'm migrating a Windows server system to Unraid (7.0.1 on Dell T440)

I have a 4 drive external USB3 docking station that I use for swapping drives to off site backup.

These will not be part of an array, but mounted as individual drives. Portions of the main Unraid array will be synchronized to these offsite backup drives periodically.

I would prefer to make these drives directly controlled by Unraid, rather than make them local to a VM.

With Windows, there is a process to unmount and remove active drives.

In Linux there is umount.

In Unraid, for a non-array drive, would unmounting it for power down and removal be as simple as

$ sudo umount /dev/sdc1

Or are there other factors to consider in the Unraid environment?

You typically use the Unassigned Devices plugin, external drives will show there with a mount/unmount button.

Just unmounting is fine, but you can also use the "detach" button from UD to power it down before removing.