iPhone backup takes too much space
I created an account just to answer this question.  I ran into this issue myself months ago and was unable to find an answer.  The short of it is, Apple is backing up things even if you have them disabled.  In my case, Messages was completely disabled from iCloud backup.  In fact, almost everything was but my initial backups kept saying 4.4GB or so.  I looked at my storage and noticed the closest to that were my Messages.  So as a test I deleted a top conversation that was over 1GB and when I recalculated my iCloud backups, sure enough it dropped by a gig.  

So great job to Apple backing up something I explicitly disabled.  Thankfully I resolved this issue on my own doing testing.  I hope this helps others.