There is some good info
HERE. You can adjust the instructions for your particular setup if you choose to go this route. If you only need CP you can skip the other softwares obviously.
At some point in near future I think the "plugins" are not going to be (officially) maintained any longer. The choice has been made to steer a course for docker containers. So you should at least give some thought to learning to install "plugins" manually in a jail. Its really pretty easy, and once you get all these to work you can install any BSD software ports in these jails, the same way. It basically walks you through how to set up whatever NAS related software you could want IN THE SAME JAIL, running as the SAME USER. I group mine based on uses. Trust me its the only way. Simplifies permissions, and storage mounting to the Nth degree. With that said, you will no longer have sliders and such to tell you when its on and all that fanciness. You will do all of your configuring and checking and such over SSH/jexec. But I can attest, if you follow the many different suggestions in and around this forum on this subject, you will rarely if ever, have to manually start/stop any of the "plugins". They start when you boot the machine (jail) and stop when you shut it down.
I cannot tell you anything about the plugins as they are in the GUI, as I dont use them, but if you were able to run
service couchpotato start
from the CP jail terminal, it will either start, or it will tell you it cant start and why. It might be as simple as the couchpotato.pid file already exists. I get that on Headphones once in a awhile for reasons unknown. But it always starts fine after I remove the stale headphones.pid file.
Also curiously, my CP runs on port 5050 not 8083. Not sure if I did that by design or not. Also, instead of this :
http://192.168.1.6:8083/plugins/couchpotato/9/_s/status, you should only really need this:
http://192.168.1.6:8083