visiting munich 24-30/12

hey everyone! we’re visiting with my boyfriend (both 30yo just for context) and i was wondering which day trips are the most worth it? we were thinking of salzburg, neuschwanstein, mittenwald, but the options are endless so i wanted a local’s pov as we’re visiting for the first time. also, how many days do you think we should spend in munich and how should we spend it? i know im asking for a lot but thanks in advance😅