Typically if you have a decent cpu then one transcode stream can be handled by one core. I have noticed in the past that one stream can light up 6 or 7 of my available cpu threads unnecessarily. Only one cpu thread is typically needed to transcode one stream, and restricting a transcoding job leaves the server with some cpu cycles for other things. I have written a script to adjust the xml profiles in Plex so that one cpu thread is used when transcoding.
After each plex server upgrade I was manually adjusting the xml profiles, and it got to be a pain, so I wrote a script to do it quickly.
The script will also backup the original files in case you want to put things back to the defaults. Attaching my script to this post, feedback is welcome.
I have not tested this script on Windows, Mac, BSD, etc, but it should work properly if you change one line to point it to correct directory.