Looks like PD spec varies voltage all the way up to +48V which supports 240W of power, so 5A@48V. Using a calculator like at https://www.omnicalculator.com/phy

Looks like PD spec varies voltage all the way up to +48V which supports 240W of power, so 5A@48V. Using a calculator like at https://www.omnicalculator.com/physics/wire-size https://www.omnicalculator.com/physics/wire-size a 1m cable with a relatively user friendly max wire temp of 40c asks for a diameter of 0.6mm. Looks like there is 4 VBUS pins and even tho it's reversible I imagine for full power it requires all 4 (or all 4 must be connected to "support" the spec). In theory you could have reduced wire diameter and spread current across the 4 VBUS wires, or have a single wire of the correct diameter and then connect to all 4 VBUS at the connector but everything is stranded wire in those cables anyway and I assume there's some complex maths to do to figure out the best for it. It is super freaking cool, though. It makes me wonder if many household appliances can't just use usb c. I don't know how much further they can raise the voltage beyond that though seeing as there's all the electrical safety rules on conductor spacing etc to avoid arcing/flash over.