Length is what matters, not punctuation. Four or five unrelated words make a password that is easy to remember and slow to guess; a short one with symbols in it is neither.

What you write is encrypted with this password before it leaves your device. There is no recovery: if you lose the password, the writing is unreadable forever.

Titles, folders, images and metadata are encrypted too. The server can see how much you have written and when, but not what it says.