Only sessions where you've turned the AI Note-taker on will generate a Journal. If you skip the opt-in or turn it off in your settings, the session proceeds as normal; it just won't be transcribed and summarised into a Journal for you.
Video recording is separate from Journals. A session is only recorded automatically when everyone in the session has explicitly turned the AI Note-taker on. If anyone has it off, or simply never turned it on, the session is not recorded. Group sessions are never recorded automatically.