You cannot come to Romania and not visit the capital: Bucharest! Plus most planes land at Bucharest International Airport, so it’s a pity to miss it! Here’s my suggestion for Bucharest 3 day itinerary. I mean 3 full days.
Day 1: Ceausescu’s Palace (half a day) and Old Town (half a day)
Day 2: Therme Spa and shopping in Bucharest