Is video editing external storage more likely to be shared 10GbE NAS or direct attached Thunderbolt 3 with software RAID?

NAS in any reasonably sized shop.

Is there a prevalent vendor/stack, e.g. Netapp, QNAP, FreeNAS, Unraid?

We use a system from https://www.editshare.com

Stornext. The poster above mentioned NAS, but I reckon it would be seen more often as not connected to a SAN.

No prevalent stack AFAIK, but add Synology and WD Nas to the list.

The kinda places I see these going in would not touch either of those products. They are both seen as the most entry level of storage devices

are we talking about workstation nas here? we have nothing but praise for synology performance and reliability. software is stable, tiering works flawlessly, expansion is inexpensive, web ui is good, ssh gives you a proper shell - do whatever operations on your nas locally, faster.

Editing workstation NAS, different IOPS use case. I ran a Synology as a test with VMware and even though the unit was certified, it was nightmarishly sluggish. That said, they're perfect for Most business not in the editing space.

I was talking storage solutions for video editing. They typically use vendors building solutions to cater for that market.