One of the things I do is set the "Custom Rating" field on the movies that I want to wait until they are older (or younger). Perhaps you want to let them watch the MCU before they turn 13, change it down to PG. Or you want to up the 1969 "True Grit" from it's original G to PG or PG-13.
I had previously tried using the tags with the restrict items set to "Allow only items..." and would put each of my kids names in a separate tag, then add that tag as I added movies, but it definitely became a management nightmare. But this may be what you are looking for with #2