Marc,
In the UE4 integration, you'll find a Wwise_UE4_Integration.chm file (there is a Japanese version as well). This should contain the information you're looking for, and all of the API. Also, the UnrealWwiseDemoGame should show you examples of passing this information (I'm not sure if it's both in code and in Blueprint). If you open the CHM and it appears empty, that's just Windows trying to protect you from the evils of the outside world. You can right click on the file, go to Properties and 'Unblock' the file. Then, you should see all of the contents.
Hope that helps!
@AKMikeD