Backup with root and restore without root
No, restoring the app-data from a backup of an app that has allowBackup=false will not work:

Helium uses AFAIR adb and if the app declares allowBackup=false you can neither create nor restore data of that app via adb backup.

Titanium does only work if the phone is rooted independently if you want to create or restore a backup.

The only chance to create a backup of an app with allowBackup=false is if the app provides an own backup/restore function within the app.