Evernote (EN) and Onenote (ON) are not calibre alternatives, so metadata as such and conversion don't exist, they don't have any equivalent to format files - everything is in their databases. And they're not word processing alternatives.
They are information organisers based around notebooks. A note can be something you write, or you copy from elsewhere - e.g. a newspaper article, a wikipedia entry. Within a note there can be links to other notes, webpages, files etc and you can embed pictures, pdfs, etc.
There's lots of material on the web about using EN and ON in creative writing projects. Search for 'using evernote for creative writing' and 'using onenote for creative writing'. Here's one that might interest you -
Creative Writing With OneNote & MineCraft
And there are lots of blog posts from writer's who use EN and/or ON for research and Scrivener for the writing:
Using Scrivener and Evernote to Write Your Book
Why One Note is One-Derful for Writers
What formats do you use in calibre?
BR