Ghost(Pro) subscriptions include hosting for one Ghost publication.
If you need to create multiple sites each with their own domain, you would need to create separate Ghost(Pro) accounts that each have their own subscription.
Each account would also require it's own unique email address, or an alias of your existing email address used with other accounts (e.g. youremail@email.com, youremail+1@email.com and so on).
Can I post different types of content on the same Ghost publication?
If your use case is to share different types of content on the same website, this can be achieved using custom content collections in your theme, or using automatically generated tag archives. This is a great option when you need to separate different content types, for example a blog and a podcast.