*NEVER* pull the plug on a NAS, unless you have no other choice.
If you want to power it off, you need to log into the Web UI and do it from there.
There’s also diagnostics in the Web UI you can access that show the drive health.
File System Checks (fdisk, which is akin to chkdsk) are run periodically on boot up, so there’s no need to do it manually.
Tony makes a good point, it is never a good idea to just pull the power on a drive. . . The drive is very robust though, and I have pulled the power on mine multiple times without a problem. Although, I would never do that with a " mission critical" device.
Being a network drive you don’t have the same type of connection that you do with a USB, so you don’t have to worry about changing settings to make it faster vs. safer. It works only one way, which is pretty safe.
As far as checking the drive for errors, there is the Diagnostics that can be accessed through the Web Interface (setup). It will give you a pass/fail.
If you are comfortable with Unix you can SSH into the drive and run more stuff from there, from the command line.