Hey Zheng,
We try to keep the posts about travelling to a certain country in one place, to make it easier for users to find all of the tips in one place so I’ve moved your post here.
Although I can’t be 100% sure, I’m very confident that, that’ll be the better option - you can compare Monzo’s exchange rate with the rate of the local money exchanger’s here though (Monzo don’t add any fees on top of the MasterCard FX rate) -
That would be the better option for Monzo, as it costs them money when you withdraw cash from a foreign ATM. But I usually withdraw some cash too & also, carry another card, as Monzo’s still in beta.