Just external - I know it's not the best solution. My setup grew on a tight budget over the last 10 years and for me it was the easiest, most affordable, and extendable/replaceable way. I don't need super fast drives in my home and I don't need backups for most of the data stored on a media server. So it kind of is just a bunch of disks with a NUC.
The internal drive for the system is an SSD though. Came with the computer.