Preferences or Outgoing WS-Security Config - use what ?

I have test requests that require certificates from a jks for SSL connection and digital signature.
I manage different projects with different certificates required for the test requests.

I notice that in SoapUI there are 2 places where you can register jks information :
- Preferences, SSL settings tab
- Within a project, the Outgoing WS-Security Configurations

What is the link between these 2 areas ? Do the preferences settings override the specific project settings ?
I would think that if I remove everything from the preferences so that it becomes blank, that my test requests would use the certificate settings from the project Outgoing WS-Security Configurations ? Apparently however, this does not happen. They strangely enough seem to continue the settings from the preferences that I have removed. I have been told that I should enter the certificate information twice : once in the Outgoing WS-Security Configurations, and the same info in the preferences. Is that correct ? I would think that is far from efficient, because then I have to change the preferences for each project with different certificates each time I switch project.

Please advise.