I said IF possible. Calm down. ^^
Also, it doesn't really matter which slot he uses. I showed that above.
In the PCIe x1 slot, or in a PCIe x16 slot...he's still only going to hit ONE Lane. The 1st 18 pins in both slots are identical.
It's also still true that without some engineer info...we don't know which Lanes are shared with the SATA ports.
In the PCIe x16 slot there are 16 Lanes (0-15). The sound card will only hit ONE of those lanes...in either slot.
I think that the only way we are going to know how this works is to actually try the sound card in the PCIE16 slot and see which SATA ports are disabled. On my MSI X470 Gaming Plus Max motherboard, if I plug something into the third PCIE16 slot I lose SATA port 1, same as using the second M2 connector. My old ASUS ROG Strix x470-F Gaming doesn't seem to have this problem. I can't find in the manual anywhere where it says that I lose a SATA port if I plug something into the 3rd PCIE16 slot, but maybe I'm missing something.
I find it a little odd that my ASUS board doesn't have that limitation when the OP's higher priced board suffers from it, but hey, that's motherboards for you.
Thanks everyone for the comments. I had some more pressing matters with my custom cooling installation but that is all fixed up now.
Ultimately I decided to play Russian Roulette. Whatever PCI slot I plug the soundcard into it will either work or won't right? I plugged the soundcard into PCIE 16 slot #3 but wasn't happy how it looked aesthetically so moved it up to PCIE 16 #2.The soundcard is working in PCIE 16 #2 without any issues that I'm aware of so far, all of my drives (SATA 1-4) are detected and working.
As for the manual it certainly is confusing and I've been informed there is further "Asus language" ahead in the BIOS settings. Perhaps I will contact Asus for further clarification.
Last edited by Kol12; 06 Apr 2021 at 03:32.
The matrix and its note are good.
sygnus21's understanding of it is correct.
(The first of the three bulleted statements is broad, refined by the statements below it.
I would reword the first : "...SATA6G-12 and/or SATA6G-34 will be disabled as follows:")
Card length does not always reflect number of lanes that a given card can use or will affect. On some cards the inapplicable edge contacts are dead, either by being unwired or by other means.
Also, a socket may contain unwired contacts by design.
And put the GPU in the last lane.... causing the OP to lose 4 SATA ports 
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