unRAID 6 is very stable. I've moved back to unRAID from a Windows server since they released 6 because quite frankly it's superb. I used to run version 5 but I'm a Linux novice and couldn't get out of it what I wanted. However since version 6 it's so much more user friendly. I currently run unRAID with a Plex and BTSync docker with a Windows 8.1 Pro virtual machine. The server has not had an issue since I set it up and I haven't even needed to reboot it, to give you an idea of stability. I'm currently @ 81 days, 8 hours, 35 minutes without a reboot and the last time I reboot was to upgrade to the latest stable release.
The linus tech tips video above will give you an idea but the unRAID forum is your best bet. You will need to research...