The golden rule about water temperature is never to use boiling water on the tea, whatever kind of tea you are making.
Herbal Teas require water at 90°C and black teas require water at 85-90°C.
Custom dictates that 4 grams are sufficient for one cup. But the amount is partly a matter of preference.
Herbal tea takes 3-4 minutes. It is a good idea to check the brewing time before making the tea because some teas need to be infused for very specific times.