Yes, you can create local notebooks. However, there is a bug detailed here http://discussion.evernote.com/topic/31517-v5-create-local-n... that forces you to create a new notebook via menu bar while in "atlas" mode to enable the option of a local notebook.

Yes. When you create a "notebook" (aka, folder) , you decide if it's local or synced. I don't think you can change this afterwords, but you could create a new notebook (with different settings), and move all the notes over.

You can set syncing to manual (and then never do it), but you still need to sign in to use the app.