Alright, I want to post some useful info for anyone else that may encounter these issues in the future.
If you find that your plugins show 0 bites in size once installed into default system directories, or that your app won't open, it means that they don't have the right permissions set. On Mac, each plugin is not a single file like on PC, but rather a bundle consisting of several files and folders, which you can inspect by right-clicking on your plugin and selecting Show Package Contents.
The reason why your plugins and apps may not have the necessary permissions is if you compiled them on a network PC. Because of the different file systems, those permissions are either not written on the PC during compiling or are unable to be copied over to Mac.
All files and folders inside the plugins packages need to have the correct permissions set in order for them to appear as plugins and not empty folders. The source files need to have the correct permissions set in order for them to be properly added to the payload inside Whitebox Packages.
Since plugins on Mac are not single files, it is not enough to simply change their permissions. Permissions for all files and folders included in these plugin packages need to be set correctly in order for the plugins to work as single units.
The correct permission are 755: Owner (R/W/E), Group (R/E), Everyone Else (R/E).
A quick way to set permission for all plugins you will be using in a project is to put them in a single folder, then set the permissions for that folder and everything inside it, thus affecting all plugins and their internal components. This will need to be done using a command line in the terminal.
To verify that the installed plugins will have the correct permissions and therefore be usable on the destination computer, do the following in the Whitebox Packages.
Right-click on the plugin you added to your payload and from the popup menu and select Expand All.
Click on each of the newly visible folders and files within the plugin and verify their permissions.
If you are missing read/ execute permission for Owner/Group on any subfolder within your plugin, it means that your plugin won't be installed properly, so you will need to set it. The best is to ensure that the source files have all the necessary permissions set so that the permissions will automatically be set inside the Packages as well.