Will we be able to know which permissions for Apple Health data the user has granted our application?
As a privacy feature Apple does not allow any application to know what permissions the user granted or denied for health data. Checking the subscriptions only tells you what you have requested to read from the system, but it can in no way inform you as to whether the user granted or denied access to a particular health data type. Please see this documentation from Apple:
https://developer.apple.com/reference/healthkit/hkhealthstore/1614154-authorizationstatus
"To help prevent possible leaks of sensitive health information, your app cannot determine whether or not a user has granted permission to read data. If you are not given permission, it simply appears as if there is no data of the requested type in the HealthKit store. If your app is given share permission but not read permission, you see only the data that your app has written to the store. Data from other sources remains hidden."