On-Premises Legacy Public Folder Coexistence for Exchange 2013 Cumulative Update 7 and Beyond

Reading between the lines a bit... As long as we do not enable MAPI/HTTP, there is no reason to go through all of this trouble, correct? (The public folder transition will be relatively brief, so it seems simpler for us to just leave MAPI/HTTP off until

Exchange 2007 is gone.)

Assuming that we do have to go through these steps anyway, I'd have some additional questions:

Why is the discovery mailbox placed onto its own database? (It seems odd to tell us to make a new database, but then to say that it's fine to put it on an existing database if we have to, with no explanation of why.)

If there is only one public folder DB, or all public folders are replicated to all DBs, then does that mean we do not need to install the CAS role? (Since there would be no referrals in either of those designs.) I don't think I'm alone when I say I prefer to

touch the old 2007 or 2010 servers as little as possible during a migration.

And you already addressed this somewhat, but if you are aware of any Outlook versions that will break after these changes, that would be good to know. Some parts of Exchange 2013 documentation still list these requirements:

Outlook 2013

Outlook 2010 SP1 with the Outlook 2010 November 2012 update (14.0.6126.5000)

Outlook 2007 SP3 with the Outlook 2007 November 2012 update (12.0.6665.5000)

Will these versions still work?