Steve, depends.
First, I don't see eight days of travel on your itinerary, so it would be quite difficult to compare your itinerary with p2p tickets vs a railpass.
If you are staying in Munich for a few days, a railpass is only valid on the S-Bahn, not U-bahn, streetcars, or buses. You can get a local MVV day tickets for travel inside Munich for much less than the cost of a day of a railpass. Munich to Schliersee, and day trips there to Füssen, Salzburg, Bayernwald can all be done with the Bayern-Ticket. For the trip to Innsbruck, both the Bayern-Ticket and the railpass would only cover you to Kufstein, the rest of the trip in Austria would be extra.
An eight day second class twin boils down to about €25 per person per day, €50 for the two of you per day. For days that you use the €27 Bayern-Ticket, or a p2p ticket if less, instead of a railpass day, you would save money, but would it be enough to overcome the cost of your trip from Frankfurt to Munich.
If you are spending a day or so in the Frankfurt area (Mainz or the Middle Rhine) before proceeding to Munich, you might avail yourself of a Dauer-Spezial fare for as low as €58 for two. But, if you want to go directly to Munich after landing, I would not advise the Dauer-Spezial fare because it is non-exchangeable, non-refundable, and your flight could be late.
If you are willing to spend a little more time getting to Munich on regional trains, you could use €6,75 (pP) local tickets from FRA to Kahl and a €27 Bayern-Ticket from there for just over €40 total for both of you.
One other thing to consider is that the Bayern-Ticket can only be used on regional trains after 9 AM on weekdays (after midnight on weekends).