I don't think the previous version had sub heading underline. Anyway, there is a `Custom CSS` in `Settings`. Check it out.
Take sub headings(h2, with ##) for example, append following syntax to the end:
h2 { text-decoration: underline; }
One of the reason the fonts don't look clean is its color. You can change it to black:
body { color : #000 }
besides, you can change the font size by check `apply font size to evernote` in settings.
Obviously, I need to write more documents about how to use Marxico better.