If your ability to add a GPU card is a requirement, Synology will not be a candidate.
Their NAS offerings do not allow that level of expansion.
On the QNAP side,
(My apologies for this screenshot of my current Guide reconstruction efforts)
If you’ll be burning in subtitles, you’ll probably want to favor the i5 / i7 processors because all subtitle burning is performed by the CPU.
I have the now-discontinued TVS-1282-i7-64GB. It’s a beast and I’ve never needed an external GPU card even though the capability exists.
