To put it simply, Smart Templates concerns the layout of your materials in an intelligent manner (graphic charter and blocks), whereas Smart Content concerns the substance (texts, translations, objects, preheaders as well as image generation).
Both can be used jointly or independently. Using Smart Templates does not require you to use Smart Content, and vice versa.
As of today, Smart Templates is available on:
Sarbacane Campaigns for creating email campaigns
Sarbacane Pages for creating landing pages
Sarbacane Forms for creating forms.
Smart Content is available on these same applications in the Suite, also including Sarbacane Studio and Sarbacane Sendkit.