What is the difference between PCIe Gen 3 and PCIe Gen 4?

m 2 4 0 in 3 0 slot   Dan m2_1 slot

First of all, I know that a PCIe 4 SSD NVMe will be running at gen 3 speeds and bottlenecked by the PCIe 3 slot But I'm wondering if there are

As the subsequent iteration of Gen3, Gen4's data transfer rate is twice that of PCIe Gen 3, enabling PCIe Gen 4 devices to transfer data at a faster speed  Gen 4 is faster than Gen 3

slot cleopatra free 2 supports both SATA and PCIe, an module may only be inserted in either one of the two interfaces, so check your motherboard documentation 3 - Real World und Workstation, 4