The 3200G's PCIe configuration is 8+4+4 - 8 lanes for external graphics, 4 lanes for NVMe, and 4 lanes to the chipset.
These lanes are all PCIe 3.0, so if you installed a PCIe 4.0 NVMe drive, you will be limited to PCIe 3.0 throughput which is half of 4.0's. But unless you are doing something that needs ridiculous I/O bandwidth, PCIe 3.0x4 is more than fast enough for typical desktop usage.