When using a charger with >27W, what is the power given to each item?

When reading about the Magsafe Duo Charger, it says that when you use a >=27W charger that it will supply 14W to the phone. Is the rest of the power (~13W?) sent to the watch side?

Also, what is the power to count as quick charge for the watch? Is it 18W based on the articles about how to fast charge your apple watch?

It sounds like to me that you can get really close to the suggested 15W of wireless fast charge on the iphone, but you will not get all the way to the wireless fast charge on the series8+ultra.

Ideally Apple would be upfront about what power is needed for quick charge, and what happens if you don't meet the power expected (do you just not charge as fast, or does it regulate you back to 'normal' charging speed.)

Thoughts?