K8y Sandboxed Google Play is the most secure way to install apps from the Play Store. Aurora Store currently does not verify the apps it installed are authentic and come from the Play Store.
Additionally, you are not avoiding Google whatsoever by using Aurora Store. Google still gets the list of apps you are installing/updating because you connect to their servers (Google gets IP and device information) to install/update apps.
It is also highly probable that apps you install from the Play Store contain Google libraries that are sending data to Google anyway.
So what are you actually achieving by using Aurora Store?
(There are some valid use cases for Aurora Store such as if a developer has their app's Play Store listing as requiring Play Integrity even though it actually doesn't enforce it. You would be unable to install such apps from the Play Store on GrapheneOS but will be able to do so on Aurora Store)