I got a 32gb note 4 that's full, also need an external to backup since my laptop is full. My memory card is 64gb and has 31gb free. I guess I could delete excess music 1400 songs and like 15k screenshots.
Do you really need 15000 screen cap images on you phone? Clear and declutter whatever you don't need.
Pics, music and video files are best stored on SD card (or multiple large SD cards). Leave the actual app files on internal memory (its faster than SD). Many apps need to be on internal memory too, and its not possible to move them entirely to SD card.