The fine print on Z690 no one seems to care enough to publish and test:
CPU:
- 1 x M.2 connector (Socket 3, M key, type 2260/2280/22110 PCIe 4.0 x4/x2 SSD support) (M2A_CPU)
Chipset:
- 2 x M.2 connectors (Socket 3, M key, type 2260/2280/22110 PCIe 4.0 x4/x2 SSD support) (M2P_SB, M2Q_SB)
- 1 x M.2 connector (Socket 3, M key, type 2260/2280/22110 SATA and PCIe 4.0 x4/x2 SSD support) (M2M_SB)
- 6 x SATA 6Gb/s connectors
Support for RAID 0, RAID 1, RAID 5, and RAID 10
* Refer to "2-7 Internal Connectors," for the installation notices for the M.2 and SATA connectors.
Intel® Optane™ Memory Ready
* System acceleration with Intel® Optane™ Memory can only be enabled on the M.2 connectors supported by the Chipset.
You'll get full PCIe4 speeds with just one NVMe as it's using the CPU link, but the rest use the DMI and sATA connector's allocated bandwidth to keep up. Also shared with the USB3 bandwidth provided (why some boards come with less USB3 full-speed links).
Not necessarily a deal-breaker, but it irks me when it's not mentioned anywhere.
Regards.