I just used foil insulation from Bunnings. Cheap, held in place by wire strung across the roof members. Personally I avoid metal roofing as it is heavy and as you guessed condensate forming; I used corrugated polycarbonate roofing, Suntuff brand, guaranteed for something like 15 years, comes in colours and has some translucency which can be useful.
https://www.bunnings.com.au/suntuf-s...ofing_p1015729