Question about Corsair Vengeance Low Profile

Replacing or upgrading with the RAMs specified in the Memory QVL will probably be very difficult; most of these items are no longer produced by the manufacturers.
On the part of the mainboard, the following is required: DDR3, 240 pin, maximum 16 GB, above 1333 MHz is OverClocking range, CL 7 to CL 9.
The question arises as to whether it is better to work with a kit of 4 or with a kit of 2.
Example 1333 MHz:
Listed at Asus is Corsair CMX8GX3M4A1333C9 consisting of 4 x 2GB.
Available at Digitec: Corsair CMX16GX3M4A1333C9 consisting of 4 x 4GB.
It is quite possible that this kit will work, especially because no OverClocking can be done with it.

Regarding Corsair Vengeance LP (2x, 8GB, DDR3-1600, DIMM 240) with CL 9 it is possible that it could work. Whether someone has tested this exact kit is less likely; perhaps one would have to search the Asus and Corsair forums for an answer; also look at the corresponding English-language forums.

Another question also concerns the operating system:
The mainboard provides drivers under the conditions of Windows 8.1 / 8 and Windows 7.
At what point will these operating systems be "phased out" by Microsoft?
Is it still worth buying a new RAM kit for this mainboard?

Super!
I also think it's very good that you announced the result with G. Skill Ripjaws.