I have one of those. I forget what brand mine is (I'm on vacation right now). Very handy. But all you need to do to test and format the drive is to open up your computer and temporarily cable the drive to the computer.
Depends on the computer.
Likely not easy to do with a notebook.
My desktop is fully loaded, so not easy to do.
I've done as you suggested with SCSI drives by using an unused connector.