NVMe is built on PCIe, so latency wise, they will be limited by the PCIe latency (roughly an order of magnitude slower than the memory bus though pcie 5 may be

NVMe is built on PCIe, so latency wise, they will be limited by the PCIe latency (roughly an order of magnitude slower than the memory bus though pcie 5 may be smaller than that) + media latency. Throughput wise, they are limited by the number of PCIe lanes that the controller supports, and the system it plugs into has been sized to allocate.