if the phone is not rooted, very little is backed up.
ask me how I know.
Contacts, SMS, the apps that were downloaded only... I never back up pictures... except to a personal PC separately.
all "real data" is lost. For Contacts, I found that sending your Contacts to a .vcf file/Printed Sheet of paper is invaluable.... you would be surprised at how much info is not included in backups.
you better export as much data from each app as you can separately.....
also, if you want the Home Screens to be retained, better use a good Launcher such as Nova Prime....
at least with Nova, I was able to export the Home Screens to my email.
Then when I added a Note 4 as my personal phone, instead of the S5, I just made sure all the apps were on the Note 4 and updated.... then I imported the HomeScreens from the Nova backup..... less than 15 seconds for Nova to make the Note 4 identical in appearance and function to the S5.
I'm a huge Nova Prime fan.