It shouldn't take long, and it follows the same principles as any other data privacy audit: Check which data is being collected, which parts of it are public, and how many of your apps can access to it.
Note that the permissions on the next screen will be split up into write permissions—the app can add data to Apple Health—and read permissions, which means the the app can take and use data from Apple Health. You have the option to disable any permissions, to disconnect the app completely, and to fully delete all the data the app has collected—at least in terms of what has been shared with Apple Health.
Is Apple really a privacy-first company?
Speaking of deleting data, pick Devices from the previous menu, then choose a device from the list, and you can erase everything Apple Health holds on you with a couple of taps. You can also delete individual records, rather than everything at once, by selecting the individual categories listed.