An HTPC or Mac will direct play the video.

A Popcorn Hour will playback everything directly. On the Apple TV 4k (any modern iOS device) Infuse will playback just about anything directly. The standard Plex player uses a player's native playback engine, if the playback device supports VC-1 playback then Plex doesn't have to transcode it, it will play directly. The transcoding that Plex does is related to the playback hardware and software. What are you actually using for playback? My son really likes SW-TCW, as do I, however, the fact that I have to dig out the BDs and play them 'old style' in my Sony X800 bothers me big time as one of the main reasons I purchased my NAS was for its (lacking?) media center capabilities.

However, I don't see an option to do a codec change in this software. I have MKVToolnix on my machine and use it frequently to convert various file formats into MKV, set deafult audio, subs and so on. I have no desire to change anything BUT the codec but I wish to do so without loosing quality.

Is there a program for Mac that let's me re-encode from VC-1 to say, H265 or anything Plex (and my NAS) can actually handle? I have read guides using Handbrake but those seem very technical for a guy who knows nothing about (re)encoding of video. Problems is that some episodes (basically all from Season 1 and some from Season 2) have the VC-1 codec, which means they are basically unplayable from / on my NAS (DS918+, 4 gig RAM). I have ripped Star Wars - The Clone Wars Season 1-5 for my son (and myself) to enjoy via Plex. I enjoy MakeMKV for ripping my original discs to my Synology NAS / Plex server.

Ds416play plex