A USB-C cable rated for 240W can still cap out at 480Mbps for data. Power ratings and data ratings are separate specifications carried by separate wires. Here is how to read e-marker requirements, speed tiers and length limits.
Thunderbolt 5 guarantees an 80Gbps link and 64Gbps of PCIe through certification; USB4 only has to clear 20Gbps to meet spec. The headline 120Gbps is four lanes redistributed 3:1, not a faster pipe.
A USB4 logo does not guarantee 40Gbps — the specification's floor is 20Gbps. Thunderbolt 4 mandates 40Gbps and Thunderbolt 5 mandates 80Gbps. Here is what actually differs behind the identical USB-C port.