There are a couple of different ways to uninstall PFS Products from Final Cut Pro.
Manually Uninstall Products
To uninstall PFS Plugin templates from your Finder, you would navigate to the following path in Finder:
Macintosh HD > Users > Your User > Movies > Motion Templates > (Titles, Generators, Effects, Transitions)
In the Titles/Generators/Effects/Transitions section of the Motion Templates, locate the folder that has the name of the plugin you want to uninstall.
Select the folder and drag it to trash. You may notice that some plugins will have a folder in multiple locations of the Movies.
Note: Do not delete the Titles, Generators, Effects, or Transitions folders, only delete the plugin you want to remove from these folders.
Uninstall a Product from the PFS APP
To uninstall a plugin simply click the three dot menu on an installed product within the PFS APP and press uninstall. This will immediately remove the plugin from your Motion Templates folder. You can then reinstall at anytime.