We are planning to go to Munich a few days early before our tour starts. Just wanted to know if the Residenz is on the old town tour or St. Peter’s church. Don’t want to see the same thing twice if they are on the tour!
Although I'd assume that the Munich walking tour is the same across the different Steves' tours that stop in Munich, I don't know that for a fact, but did do the walking tour as part of Germany/Austria/Switzerland in June 2018.
From my recollection, walking tour did include Alter Peter (at least outside) but don't recall if we went inside. Was there again last month and did the climb up the tower. It was a long climb that required some waiting and navigation as other went up/down the narrow steps, but I'm very glad that I did it and would recommend. I don't think you'd regret seeing it at a leisurely pace on your own time. The tour would just give a different sense/perspective.
I didn't see the Residenz as part of GAS, but had been there before. I would recommend that. Give yourselves a few hours to include the treasury, too.
On our free afternoon of the tour, my nephew and I went to Nymphenburg Palace and had a good experience there, too. Lovely to walk the grounds in good weather and lots of interior stuff to see as well.