Question on Site Scripts, Site Designs and Content Types

Chad_V_Kealey Enterprise Content Types does indeed refer to out of the box content types and not content types you have created. However, I would highly suggest to not use the Content Type Hub all together as it as significant delays at scale, and they won't work well with your site designs and site scripts.  If there is a scenario where you need centralized managed values in your columns, I would use the Managed Metadata Fields. Otherwise, I'd keep your content types on the site level and deployed through a Site Design.

The limit for Site Designs is 100 and the limit for Site Scripts is 100. This should be a large enough amount to account for most structures in an environment. Depending on your size, if you have more than 100, I may question the IA that is being put into place.

While technically, list templates are still available, this also requires turning noscript on and isn't recommended. These list templates also would not include any customizations such as PowerApps or Flow, though, neither does Site Designs and Site Scripts.