> It's more bandwidth to the chipset, meaning you can run double the PCI 3.0 gear off of that chipset than you could before without hitting a bottleneck
Not necessarily the case in practice since that would require some sort of chipset or active converter exposed by the motherboard to mux 3.0 lanes to bifurcated 4.0 lanes. A 3.0 x4 device still needs those four lanes to get full speed so in a PCI-e 4.0 setting you’ll actually be using up four of the PCIe 4.0 lanes, but inefficiently.
Not necessarily the case in practice since that would require some sort of chipset or active converter exposed by the motherboard to mux 3.0 lanes to bifurcated 4.0 lanes. A 3.0 x4 device still needs those four lanes to get full speed so in a PCI-e 4.0 setting you’ll actually be using up four of the PCIe 4.0 lanes, but inefficiently.