WD model - PLEX compatibility

Good morning,
as per title, I am interested (6TB - 2 bay capacity) to MY HOME DUO or MY CLOUD ULTRA EX2.
officially in the WD documentation both would support PLEX; I would say support because in the end in the PLEX compatibility documentation it would seem that only DUO is able to play movies being able to transcode them because of the CPU realtek, while the other not … (for the EX2 should have a certain format … to be played ) … (I have over 1000 films in MKV format with H264 codec and AC3 audio).
someone could help me to understand what may be the best choice between these two and if what I wrote (because read on the net) is true?
I can not change the model because of the budget I have available and the only deals with included disks that fit into my budget (and compatible with PLEX) are these.
thank you all.

The article below shows what the my cloud home supports as far as transcoding.