Yeah, but still much more reasonable than buying more Odroid boards that would also require multiple power supplies and ethernet connections
To just use a max of 4 drives, for an home NAS, Unraid is overkill in my opinion. Even just a RAID1 NAS to back up photos, videos and some documents is a decent solution for an home.
With the HAT you’ll have 4 ports. If you start with the Odroid is one drive and that’s it.
Unfortunately I don’t think there are many other viable solution going with an SBC since they’re not made to be NASes but more like for connecting sensors, motors and so on.
I used OVM on my Pi2 overclocked with Nextcloud, PiHole, Transmission and one drive shared on the network. I didn’t have much issues with it but a friend with a Pi3 had some like you did. I don’t know at this point if it’s a problem with the OMV image or not. I know a sample of 2 isn’t much but it’s something.
If you want to give the possibility of expansion you’re forced to get an x86 machine, buy an Unraid license and give it out. But that would cost you at least 300$.