I've brewed a couple variations of a Munich SMaSH. I always kind of followed the Munich Dunkel guidelines for gravity, abv and IBUs. Something about 5% abv that finishes around 1.013-1.014 with about 25 IBUs. I usually use magnum to bitter (20 IBUs at 60 mins) then use a noble hop at 10 mins. I know that technically makes it not a smash beer, but magnum is pretty neutral so you're really only tasting the noble hop. I personally prefer Tettnang.
I also usually use a lager yeast when working with these ingredients, but a German ale yeast would also be a good choice - wlp011, wlp029, wlp036 would all work.