DIM strips all the subfolders from the Content folder and places them where they belong. DIM also creates a new default DAZ content folder called My DAZ 3D Library; that folder must be linked manually to DS otherwise you will not find any of your installed content. You can also use DIM to install Poser content, a feature that many Poser users are not aware of or don't know how to use. If I download anything from DAZ that is my preference, I have no problems with it.

Depending how old the content is and whether it has been updated, it may contain rsr formatted files whose proper thumbnails will not show up. To verify this, you will need to open explorer and check what you have in that folder. The other issue is that those files might be DAZ formatted files that typically inhabit the runtime folder.