garry You can simply avoid granting Microphone access to apps. There's also a global Microphone toggle which you can disable to disallow access even for apps or OS components with microphone access. It works the same way for the Camera permission and toggle. There's also an access history and indicators when they're being used.
Location is also largely the same but more complex since it has an additional tier of permission grant for background access that's not supported for Camera or Microphone which always require apps to be in the foreground. Location also allows granting only coarse grained rounded location estimates instead of precise access.
The only difference on GrapheneOS in this area is that we finished up the Location indicator and access history features. The stock OS only has an experimental developer options for a Location indicator and doesn't include all kinds of location data requests as part of it or the access history.