Program for automatically reducing file once recording finishes on Mac

I’m looking for a program or anything for my Mac that will automatically take files once plex records them and reduce the file size. I see MCE buddy but not sure if that is for the Mac and I’m not sure with handbrake how to ask it to automatically reduce a file size when something new shows in a folder. Any ideas with this?

use Handbrake and convert to .mp4 with the Apple TV settings (if you use Apple TV).

Yeah I like Handbrake but is there a way to have handbrake automatically convert it once plex finishes recording the file?