I’m an iphone user and I’ve always used Dropbox and google photos as my general backup mediums.

Isn't that photo specific backup rather than general backups? Last I tried, Dropbox on iPhone cannot backup any files owned by other apps automatically. You'd have to export it manually to Dropbox.

Edit; It looks like this is possible on iOS for apps to access other app's file sandboxes with a somewhat recent iOS update. MobiusSync (Syncthing client for iOS) has beta support for it. But I see no mention of Dropbox adding support for anything similar