Custom font and CSS?

Hi there,
I have several questions before I consider buying this plugin. First, I would like to use a custom font family for the emails. How can I do that? Second, I would like to apply modifications via CSS. I’ve seen the CSS field, however, I didn’t manage to apply CSS to specific elements. I looked up the html descriptors with the browser inspector and applied a text color but that did not work in the test email. Besides, I don’t see the switch between “Visual” and “Text” to be able to work with HTML code. How can that be activated? It’s a pity that I have to ask this again as there are the same questions in the forum, which I’m not allowed to see.
Thanks in advance!