Magic Item Limitations

The Concern

How many and what kind of magic items can be used at once? Can a character wear multiple necklaces? What about cloaks, or armor? Rings?

Details

RAW: "A magic item meant to be worn must be donned in the intended fashion: boots go on the feet, gloves on the hands, hats and helmets on the head, and rings on the finger. Magic armor must be donned, a shield strapped to the arm, a cloak fastened about the shoulders. A weapon must be held in hand."
...
"When a nonhumanoid tries to wear an item, use your discretion as to whether the item functions as intended. A ring placed on a tentacle might work, but a yuan-ti with a snakelike tail instead of legs has no way to wear magic boots."

Ruling

As RAW, for the most part - in order to benefit from the magic item, you generally need to wear or use it "as intended." However, it's not always crystal clear how many of something one can, in fact, wear as intended. Two necklaces is probably fine - two cloaks seems like it wouldn't work, though. Any item requiring attunement is a prime candidate for not working with other magic items in the same spot.

I'm willing to be flexible on this (and potentially homebrew items to get around it, on request) but there is a limit - please don't go exploring for it.