Poser 11, 12 & 13 All have a folder setup that says Poser XX Content.  Where you place that folder is up to you.  Me, I have my setup to be E:Poser Content: Poser XX Content.  All my external runtimes are located in E:Poser Content folder so I know where they are.  The ONLY thing that is added to Poser XX Content is the required content to make Poser work and that would be in Poser XX Content:Runtime. Then you have Downloads, Included and Purchases.  Those are folders that sit next to the Runtime folder and inside each of them is their proper Runtime folder where the content lives.  IF you don't want to use the included or Purchases folders that is up to you.  I use them to download content and move it to another location.  And that location is a Runtime that is NOT Poser XX Content, Purchases, Included or Downloads.  However doing testing on Poser I tend to leave the Included content where it is to be more like a first time user would experience.  

Poser's indexing on the  content libraries is fast enough now that moving content from runtime to runtime is not painful and the search function will be updated before I close out of a session.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13