The PLIST files themselves aren't doing anything, so a change of direction is in order. I would shut down and boot into Safe Boot Mode by holding the SHIFT key at power-on for 30 seconds. In Safe Boot I'd download https://malwarebytes.com and do a scan. A lot of times it's adware and such in the background that is causing your system to be running unwanted things.
After you do a scan and remove anything it finds I would go to > System Preferences and open the Users & Groups icon. Click on your user account and go to the Login Items tab. This will show you the legit programs (as opposed to adware, etc.) that is loading automatically at startup. Your Mac itself doesn't need anything here. Unless you recognize anything you want to specifically keep from starting automatically every time you can click it, and click the minus ("-") button below to remove it. This won't remove the app, you can still run the app if you want, it will just keep it from starting automatically every time whether you want it to or not.
Once you've done these simple steps to clean up your system you can restart normally and see how your system behaves. If it's still behaving badly you can post that here for more information as to additionally steps to figure out what is going on.
Specifically, the next step is to launch the Activity Monitor app and to see what is taking up the most CPU usage when everything is closed. The bottom graph on the CPU tab shows your IDLE and you should be well over 90%+ idle with everything closed on a fresh boot.
