Which end is host in a USB-C to USB-C charging/power cable?
Type-C cables don't have gender, they are "they", symmetrical :-) They do have a wire CC (communication channel) that conveys who is who between devices.

In simplest basic case (no Power Delivery), if you have both devices with Type-C connectors, one "provider" (charger), and another "consumer" (a phone), the provider should supply proper pull-up resistor on CC pin indicating how much current it can supply. The pull-down on CC wire will be provided by consumer (CC pull down inside the phone). This is the way how a charger tells the phone how much "juice" the phone can take.