If you wish to uninstall any trace of the Sonarworks measurement application or plug-in, just launch "Programs and Features" on Windows, select anything Sonarworks and uninstall as you would with any other application on Windows (preferred method).
If you wish to remove the files manually, here's a list of the directories, where you can find the corresponding files:
C:/Users/<user>/AppData/Local/Sonarworks/Reference 4/Sonarworks Projects
C:/Program files(x86)/Common Files/Digidesign/DAE/Plug-Ins/Reference4.dmp
C:/Program files(x86)/Common Files/Digidesign/DAE/Plug-Ins/Reference4.dmp.rsr
C:/Program files(x86)/Common Files/Avid/Audio/Plug-Ins/Reference4.aaxplugin
C:/Program files/Common Files/Avid/Audio/Plug-Ins/Reference4.aaxplugin
If you want to remove the registry files with a registry editor, this is where you can find them:
/Macintosh HD/Library/Audio/Plug-Ins/Components -> Sonarworks Reference 4 plugin.component
/Macintosh HD/Library/Application Support/Avid/Audio/Plug-Ins/Sonarworks Reference 4 plugin.aaxplugin
HD/Library/Audio/Plug-Ins/VST/Sonarworks Reference 4 plugin.vst
/Macintosh HD/Users/Username/Library/Sonarworks/Reference 4/Sonarworks Projects
Note that the Users/Username/Library folder is a hidden folder and might not be visible (as opposed to the MacHD/Library folder, which is visible by default). See this article on how to Show Hidden Folders on Mac.
To remove Systemwide, launch it and navigate to Settings. Under the General tab you'll find a dedicated Uninstall button.
If you wish to remove the files manually, remove Systemwide from your Applications folder /Applications/Sonarworks Systemwide/. In addition, remove the following files from your Library:
/Macintosh HD/Users/Username/Library/Sonarworks/Reference 4/Systemwide/SonarworksSystemwide.settings
If after uninstall process you still see Systemwide in the list of audio devices:
First, try to unload the kext file from your Terminal app:
sudo kextunload /System/Library/Extensions/Sonarworks.kext
Then, remove the kext folder so doesn’t autoload on next boot:
sudo rm -r /System/Library/Extensions/Sonarworks.kext