How do I safely remove or Hot Swap USB devices?

You can generally plug and unplug USB devices with no precautions or special tricks because USB is very robust. However, to safely disconnect a hard drive or other data storage device, you must first unmount it so it's not visible on the desktop. This closes any open files, and tells the system it is ready to disconnect. You do this by clicking the device and in the File menu of the Finder, selecting 'Eject ......', where ..... is the name of the drive, or right-clicking it and selecting 'Eject' or by dragging it to the trash - which doesn't delete anything, just unmounts it.

If you don't do this with a data storage device, you risk damaging the directory, data structure or files on it.

Yes, on a Mac you can indeed generally plug or unplug USB devices, except drives. Those can be plugged in, but as said need to be unmounted/ejected before disconnection.

Bear in mind though that it's only generally. Not because there are other rules that might apply, but because USB is somewhat finicky and prone to odd behaviors, so things don't always work quite as simply as they should. Hubs, for example, can confuse systems, particularly if used with high current drain devices, so other things then don't connect or disconnect properly. In that instance, usually powering down the hub and then back on will resolve it, but sometimes the hub itself needs to be disconnected and then reconnected.

All in all, don't be surprised to see an occasional unpredictable result with USB - not usually a problem just a glitch. And as long as you eject the USB storage device and it vanishes off the desktop, your data should not be at risk.