Looking through the notification documentation for how to capture all calls that a user would receive, I noticed that call backs have their own event, so there are two events:
Looking at the data returned by both events it looks like they are almost the same. If a scheduled call back becomes active, would you get notifications of that active "call" if you only subscribed to v2.users.{id}.conversations.calls? Or are call backs treated completely differently and does it require subscribing to both v2.users.{id}.conversations.calls and v2.users.{id}.conversations.callbacks to get notifications for all of a users calls?
Generally you can subscribe to v2.users.{id}.conversations and you'll receive a Conversation event payload. The event payload is a generalized JSON schema that is reused for all media types.
You can think of the *.calls, *.callbacks, *.chats, etc as a filter. You won't get different JSON schema payloads for each media type, but you will only get event data for those media types that you subscribe to.
To answer the second half of your question, if you subscribe to *.calls then you'll get events for inbound calls, outbound calls, callback calls, etc.