The "Developer ID Installer" certificate is what you would use if not submitting to the AppStore.
Certificates Matter
These are the certificates you will need to use together for codesigning:
- Developer ID Installer
Developer ID Application
- 3rd Party Mac Developer Installer (usually only used for the AppStore apps).
Apple Developer Codesigning Workflow Guide
In short, you have codesign your installer in a specific order with the correct codesigning certificate. I answered a similar question previously here.