Hong Kong is not the same as Mainland China – they have a different AliPay. Chinse Alipay will not work in Hong Kong and Hong Kong Alipay will not work in China. Google apps work perfectly Google Maps tells you which bus to take and where.
China eSim doesn’t work, you need an Asia and/or Hong Kong E-sim .
For payments, you need the Octopus card! https://www.octopus.com.hk/en/consumer/index.html
Travellers report that many businesses will not accept Mastercard nor Visa credit cards. Some will accept cash but will be annoyed because it’s not fast nor convenient.
Octopus card can be used for public transport such as the subway and buses, paying at stores.
You can purchase an empty card at a 7/11. It costs about 40 HK$. Then you can add money to it in multipes of 50HK$. There are 7/11 stores in most subway stations.
Chinese yuan is not accepted in Hong Kong.