the only place i know of that might set the global default is under View|Layout. if that isn't working for you, there isn't any other place to set a global default.
Whenever I create a new folder in Outlook, the preview pane automatically shows. I don't like to use the preview pane and I'd like for all new folders to not have that as a default. I know how to turn it off once it's on, but I'd like a way to never see it.