I now have a mini pc next to my NAS, and leaving my NAS to only file storage chores. That said, I also am running NVidia Shield TV Pro boxes with Kodi for local media and largely don't have to worry about the encoding.
I bought an inexpensive used Mac Mini and attached a standard HDD USB3 enclosure to it with multiple drives. Works great for streaming to any network appliance I want to use.
Transcoding was the reason I moved away from Synology. The rest was fine, not great but ... Okay
But there was no way to improve transcoding performance. If a stream lagged, it would always lag. Hence I jumped ship and just made my own