Is Prismic good for my email templating case?

Hi there!

I'm evaluating CMSes and not sure if a headless is good for my use case, which is:
I'd like to have a UI to build an email template (with variables and etc) and have a microservice querying for this template, merging data and sending out (this part is outside Prismic).

Has anybody done this here? If not, any suggestions?

This could work. Anything that needs content fields being output as JSON for consumption via the API can use Prismic. This can be Jamstack, mobile applications or other services like you describe.