rom flashing and data loss

asking for a friend who can't make the post currently on xda but he's looking to flash a rom over to his Samsung Galaxy Note 3 (T Mobile) which is already rooted. The question is would he be able to flash the rom over and then things such as Gapps ect and then restore from a Samsung kies backup? (kies essentially is a perfect backup for Samsung phones for those who aren't custom to it)
Or what method would work to not lose stuff after a rom flash? (texts/app settings ect)