> One of those is way thicker than the other, at least.

I bet there's at least one brand with extra–thick plastic insulation.

> I would love for something to force a speed and power rating on USB-C plugs.

This already exists. Cable makers can certify their cables and mark them with their data speed and wattage.

I buy only certified, marked cables. If I see an unmarked cable, I assume it’s slow and low-powered…which is good enough for some things.