The various restaurants and small shops on the side alleys. Our slightly larger resto for dinner did take MC/Visa, but our lunch place didn't. Some of the snack stands along the main tourist plaza also took WeChat/Alipay but no MC/Visa sign.

And yes, the difference in HKD and MOP are small. But I work as a financial controller, so I notice these things . It was just really half a day + overnight. Back in mainland China, so no more worries about cash or card