Does the DS918+ have enough horsepower to transcode / stream 4K videos using Plex?

I currently have a DS415play and it is under powered, i.e., many of my high bit rate 1080p movies buffer a great deal. Would a DS918+ allow me to stream 1080p movies, and 1080p home videos, without buffering? I’m also interested in a future proof solution for when I get a 4K TV.

I suggest you search in the Synology forum. You’ll find numerous threads on the performance of almost all the 2018 Synology product line.

another alternative with similar dollars to upgrading to the 916+ (even if can sell the 415play) is keep the 415 play and get a NUC or Shield pro to do the serving !!