I don't think 16tb is an exaggeration these days. I have ~ 10tb of films, 1.5tb of music, 1tb of my own projects, 1tb of programs ... of course, everything double for data backup. also space for the system and of course 1-2tb of work space. if you want to cut a film, edit a large db or do something in this direction you also need space. I have 16tb internally and 16tb externally (backup, because I also dont belief in raid for backups) and i dont have enough space for anything.
if you have more space, you will use it... but on the other hand, if you dont have much data at the moment you can buy it later...
if you are just watching movies and do some office work 8gb are enough. but if you are using cad, c4d, resolve, after effects, or similiar then it happens that you have 16gb completely full. I have never really exhausted the 64GB I have at work, but 32GB are helpful. and i don't do any elaborate things with it but use many effects or several of these programs at the same time.