Plex doesn’t usually publish plans. But there’s a feature request open for AMD hardware encoding support.
[Feature Request] Add support for AMD's Video Core Next encoding
If you want a lower powered CPU that has embedded transcoding support, consider an Intel CPU with QuickSync.
https://support.plex.tv/articles/115002178853-using-hardware-accelerated-streaming/
I’m a TrueNAS user myself, but … if you want the best/easiest hardware acceleration support, you might consider Linux. Notes from others that have gotten hardware transcoding working on FreeNAS:
GitHub - kern2011/Freenas-Quicksync: How to guide for getting Intel Quicksync working on Freenas
Consider too the support for accelerated tone mapping:
As you said, much of this may not be important if you don’t expect to use server-side transcoding. This will be dependent on your files, users, and playback devices.
