We used the bottled water to mix with the formula to feed our bb since he's about 1 month old. He was mainly breastfed, so he only had formula maybe once a day and he's fine.
We didn't boil the bottled water. We either microwave the bottled water to the right temperature to mix with formula, or mix the boiled filtered tap water with the bottled water to the right temperature.
In HK/Macau, the Watson's bottled water should be ok.