If you power your Raspberry Pi from your laptop using something like a USB-C to USB hub you will not fry your Raspberry Pi
In response to this part of your question:
In this situation which device would govern the power delivery?
Every device that supports USB-C will have sort of a descriptor table of what voltage and current it can both sink (take in) and supply (give out).
For example, My phone can sink either 5V @ 0.5 - 2A or 9V @ 1A, It can supply 5V @ 0.1A. When my phone is attached to a USB-C capable power plug the phone and the power plug will negotiate with each other about what will work best.
I just looked up a USB-C power brick on Amazon and it advertise this:
"...Charge faster, power delivery fast charge your MacBook, laptop or cellphone at the adjustable voltage and current 5V/ 9V/ 12V/ 15V/ 20.3V/ 3A, or 5V/ 2.4A, this USB C..."
If my phone were to be plugged into this device it would interrogate the power brick and find that it can supply 9V @ 3A and then request 9V @ 1A. If your laptop, that can accept 20V @ 5A, were to be plugged into this device it would request the maximum of 20V @ 3A.
Unfortunately all the pre USB-C cables cannot negotiate power this way so if you ever have a USB-C to a pre USB-C cable the maximum that will be supplied is 5V @ 0.5A (2.5W). Unfortunately, this isn't enough to power the Raspberry Pi and any devices attached to the Raspberry Pi's USB ports (which should all be able to supply 5V @ 0.1A).