Download the OS image. xzcat pipe to dd to the disk. Two partitions are created and take up about 14GB.
The default EEPROM `BOOT_ORDER=0xf416`, the boot order should be NVMe, SD Card, USB. But it still boots the SD card first. With the SD card out, the RPi 5 boots from the NVMe. The root partition is near full. Use resizepart and resize2fs to grow the root file system and it is OK is to resize at runtime.
A sustained read/write speed is 390MB/s read and 440MB/s write, which is better than the USB NVMe adapter 260MB/s read and 380MB/s write, but not dramatically.
The RPi 5 PCIe is rated for Gen 2 one-lane; the maximum throughput is 500MB/s.
In config.txt, add `dtparam=pciex1_gen=3` to enables PCIe Gen 3 (1GB/s). The reliability of the Gen 3 operation is not guaranteed, but it appears to work well. The read speed is increased to 850 MB/s; the write speed is largely unchanged. The disk is rated at up to 1700MB/s for sequential read and up to 1000MB/s for sequential write.
The board averages about 1.2A/5V during writing.
The PCIe interface appears to have some interference on the WiFi signal. The on-board WiFi has trouble picking up relatively weak signals. Other people have reported similar issue. The WiFi does work when it is close to the router.
