NAS software for video editing. TrueNAS or UNraid or custom linux?

I run a small post production company.
Our current workflow is we have Thunderbolt RAID boxes connected straight to our 2-3 workstations. We fill them up usually within a year (26TB usable) and then replace them with new ones, and keep the old ones with old projects in storage. They all have spinning drives.

This is not very cost effective.

Since work is slow at the moment I’m thinking of building a NAS to either ideally replace the directly attached thunderbolt boxes entirely, or if it turns out to be too expensive then keep working off of the existing hardware and use the new NAS as archive, so I can just move older projects to the NAS and free up space on the RAID boxes.

We have 2 full time working workstations and 1 half-time. 2 of them have already 10gbe networking.

Currently the slowest setup that is still good for daily use gets ~600-700MB/s read-write, so this is the speed minimum speed I would aim for ideally.

I have an unused i5-9500 machine which supports max 128GB RAM that I’d like to use as a base. I also have 10s of 2-10TB spinning drives laying around that I could use.

Expandability is definitely necessary - so that I can just add dries to the NAS if the old ones fill up.

Now asking for suggestions - TrueNAS or UNraid? Why? zfs or xfs or btrfs? NVME SSD RAID0 as cache?

Truenas would probably do a better job of having a robust raid strikingparity and redundancy setup. But you can’t just arbitrarily install drives in it over time, you gotta set up vdevs with all drives present. New storage would add more vdevs. I am not a zfs expert sorry

I don’t know what it would take to get 800MB write speed with zfs. Maybe striping 4 drives together is enough, or maybe it needs SSD.

Unraid lets you hook up arbitrary drives, but redundancy is usually just a single parity drive. And speed is typically limited to the speed of a single drive.

You’re going to have a lot easier time not editing directly on the NAS. Edit what you’re working on locally and build up an archive server. If simple expandability is key, go with Unraid, and either be prepared to wait for large projects to transfer over or size up a cache for ingest that can handle your needs - don’t know what those are though.