Hey bytedude!
Yes, the options for the self-hosted CSS file require that you sign up for a production account. Once you do that you will see a new menu that shows various Namespace
settings.
As for stand-alone mode, check out this FAQ: Do you have any real examples
Basically stand-alone mode is useful for a dedicated FAQ site, like this very page you are looking at!
Embed mode is for adding comments to an existing site.