So you reckon it’s my connection is bottlenecking the whole operation?
EDIT: I noticed when I’m on my home network, there is no issue with the videos being slow. So it is the connection most likely. Ergo, nothing I can improve unless I upgrade my contract?
It definitely cannot be the NAS. The NAS does not do any sort of transcoding when you play a video using the Synology Photos App. Try a lower res/bitrate video, if that plays fine, then your internet upload speed is the problem.
Is there anything to it? Is it possible that the Play series is for the Plex functionality?