New Blog Templates and Child Themes?

I would like to have standard templates setup using the New Blog Templates, with configurations pre-built. However, I'd then like to make themes, I'm guessing Child Themes probably, available for different Pro Sites levels.

Does the template override the theme? Or can users still pick a theme and apply that on top of the blog template?

There are basic setups I want to do that apply to all sites, but I don't want to have to do this programmatically in a theme. New Blog Templates would let me setup the basics, but then I need to allow users a choice of themes. Is this possible?