A significant difference is that rather than “show emails: all”, above, the selection becomes “chat reachable by: everybody”.
So it is just what one needs to receive all emails in chats, e.g. if not using any separate classic MUA.
The “max. chat message metrics” setting would have to be set to unlimited manually though, I guess, to allow showing emails of any length.
With these settings, the “new emails” counter (that allows to peak at the emails for the other cases) might even be disabled automatically, because it would only be redundant.
So your use-case should be covered.