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.