8gb is not ideal but why does pcie4 matter? 5060 is unlikely to saturate PCIE
When a game needs to use more than 8GB of VRAM, it will begin to allocate system memory. The speed of the PCIe bus impacts hoe much of a gradual performance drop you get, as well as impacts how much system memory you can allocate before the PCIe bus saturated and you end up with major issues with hitching and stuttering, or extremely low frame rates.
Since after the RTX 3000 series, Nvidia started leaning really hard into crippling the PCIe bus, we started seeing their cards struggle a lot more in those sub-optimal conditions.
While a different set of cards, when there is VRAM spillover, the RTX 3060 8GB has less of a performance hit than the 4060 8GB. While the spillover is never ideal, a faster PCIe interface makes a bad situation a little less bad (doesn't mean the situation becomes good, but it does become a bit less crappy).
If Nvidia is going to cripple the VRAM, then they should at least offer a full PCIe 5.0 X16 interface, which would go a long way to improving the ability to use shared memory.
The videocard drivers are smart enough to prioritize which memory pools are used, and do a decent job of moving assets that are less throughput intensive to the system memory, but as more gets moved over, the utilization adds up and once the PCIe bus saturates in at least one direction (typically when the bus usage hits 50%, since it doesn't read 100% unless you are simultaneously reading and writing as fast as possible), then games become unplayable..