How to test disabling automatic backups on ios and android?

I am building an app with Ionic v1, Cordova, and AngularJS v 1.5.

I am targeting both Android and iOS.

I have been advised to turn off automatic backups for security reasons.

I believe this applies to both iOS and Android. iCloud and Google Cloud.

Our app has already been in use for quite some time so some people will have backups already.

If I disable backups, will the people's backups still be there? From the past? And then it will no longer backup anymore? If there any way to get rid of the previous backups from the app? Can we do anything about the past?

Furthermore, I will need to test if disabling this will actually work and not do any backups. How can I do this?