PCIe uses different rates than USB, but both at their basics use NRZ (Non-Return to Zero) https://en.wikipedia.org/wiki/Non-return-to-zero https://en.wikipedia.

PCIe uses different rates than USB, but both at their basics use NRZ (Non-Return to Zero) https://en.wikipedia.org/wiki/Non-return-to-zero https://en.wikipedia.org/wiki/Non-return-to-zero. The bigger differences are in the channels they target. The channels characteristics drive the complexity of the signal processing circuitry required (eg Power and Cost) in the PHY devices. Hope that adds a bit of clarity to your PHY question.