Questions regarding document defaults and embedded styles

Hi!

I recently jailbroke my Kindle and enjoy KOReader a lot. I've got some questions though.

1. How does setting Document settings -> Save document settings as default differ from holding specified settings in bottom menu? I learned about the second method today, so far I've used the first method.

2. Is it possible to completely reset mentioned document settings to KOReader's defaults, in case I mess up badly?

3. What's the preferred strategy for Embedded Style, Embedded Fonts, and Style tweaks -> Text -> Font size and families -> Ignore publisher font families / Ignore publisher font sizes? I'm not sure what's recommended for most books. Simply turning off Embedded Style makes some books look bad, from my testing, but at the same time I love using Bookerly font, and don't like when books enforce their own font... What's your go-to?