So I'll be flying out next week. Arriving in FRA in the early afternoon Thursday, then Taking the train to Munich Sat morning and flying home Tuesday morning. Staying at the HIE in Frankfurt and the Schiller5 in Munich.

Still not 100% sure about what to do in Frankfurt. I'm looking into your suggestions.
As for Munich, I think I have a decent plan. BMW Museum (although the plant will be closed ), the Deutches Museum and a few other sites, Then taking a day trip to Salzburg.

I guess I should have mentioned that I'm more interested in unique museums (bmw museum, deuches, etc) or one-of-a-kind things (fancy fountains, worlds largest ..., etc) or versus old buildings (churches etc). I do plan to go for some walks to see the architecture but visiting a bunch of old buildings starts getting old for me. I was going to go see the worlds biggest ice cave near Salzburg but after reading about the hassle to get there and the poor lighting I decided to cut that from my list.