You can set the templates directory to anything in plugin.json, I think it defaults to just templates if you don't specify.
Them you match the path from views, so it would be templates/emails where you put them.
I'm looking specifically at this pull request.
The problem: Block Quote style doesn't match the style you'd see in the template.
Problem additional: Block Quote style may differ from template to template.
Current solution: A style that is a copy of the style in persona.
The best solution: A style that references the style in the template.
Anyone got any ideas on how to do that? Is it even possible? It seems like this will be an ongoing issue.
I think some of it stems from styles defined in the default less that is provided as part of redactor.