Does this include the hard drives or do you add them yourself?
You add the drives yourself. That said, large capacity HDDs are pretty cheap these days, and any NAS that includes the drives would be more expensive than buying the drives yourself anyway.
Is there a size limit to the hard drives that can be used?
They sell these preloaded with 10TB drives. I’m not sure what the limit is. I bought mine from Woot when it was onsale from Woot at this price a couple weeks ago and put 4TB’s in it.
Anyone tried Plex transcoding on it? Finding mixed reviews online.
I have a higher end QNAP 6 bay and use it for Plex transcoding, and it works great - even multiples streams at once. I can’t speak for this particular model, though. It may have lower end chips in it. In general, the QNAP NAS units are quite nice.
Quality on this model seems to be hit or miss. Anyone else notice this?
Hard to say, historically Plex has recommended x86 NAS’s for Transcoding.
However, AFAIK, Mainline Plex does not YET support hardware decoding/transcoding in these new RTD1296 (ARMv8, I believe).
There IS an alpha test release that looks to have hardware support for these - give it a shot though! (expect bumps and issues):
Specific link to Plex Alpha build with what should be HW support for this specific NAS:
https://downloads.plex.tv/plex-media-server-new/1.14.0.391-7623e9224/qnap/PlexMediaServer-1.14.0.391-7623e9224-aarch64.qpkg
(You may need to be a plex pass user for this build…)