Armadillo gets all it’s styling from the themes blog plugin styles. It was originally designed to be a replacement for the built in RapidWeaver blog plugin. Over the years it’s evolved into much more.
I don’t have depth, but I thought it should work fine with the built in blog. I’m not sure why you’re having issues with using Armadillo with the Depth theme.
As for the “plain” look you’re seeing, it’s because you are using foundations theme that was never intended to be used for the built in blog plugin. It doesn’t have any of the standard theme blog page CSS for styling the blog entries, tags, headlines, etc.
what you might do is build a small project file, and setup a sample built in blog with a few categories,tags etc. ta that small sample project and try changing the theme to different themes you have. If you find one that looks better than try publishing with it. It’s just easier to swap themes and preview with RapidWeaver and the built in blog plugin than republish with Armadillo.
I would probably try to figure out what exactly was the conflict with the Depth theme and address that firsthand.