Yes
It should be , you can run plex on Mi Box and get things arranged.
You can't run Plex server on it but you can run Kodi or Nova player.
It would work BUT if your videos size are over 4gb , it would be problematic.
My 4tb only works when connected directed (as it is self-powered)
While you should be able to you might consider looking at your router to see if you have options there. Then all the devices in the network can access it.
Being able to add/remove content from other device could be easier.
I have connected my 5 TB Seagate Portable HDD it works smoothly.