Andrea, I have a CPU 8 cores / 16 threads, but the final rendering uses only
one core.
The only way I could get my 16 core laptop to NOT use multiple cores was to set the Operating System cpu count to a lower number or to change in {path}/bin/ffmpeg, the file encode.opts from "threads=auto" to "threads=1". I used ffmpeg filetype of mp4 in my renders. Even when I set "Project SMP cpus" to 1, it still used multiple (this is in Settings, Preferences, Performance tab). Also, be sure to uncheck "use Render farm" so that the next time when you do not want to use the render farm, it does not automatically start up and surprise you.
Since I'm compiling CinGG (note: all threads are used for compiling), maybe I need to enable some flags or something like that? Are there any customizations to do? Or should I set something in the operating system?
Step 5 in the Render Farm usage just means that in the Render Menu, where you typed in the name for "Select file to render to", the 15 files will be named accordingly. For example, if you keyed in "/tmp/mystuff.mp4", you will have files in /tmp named mystuff.mp4001, mystuff.mp4002, ..., mystuff.mp4016. The RenderMux procedure uses ffmpeg to concatenate them together into 1 file called mystuff.mp4.