Your photo shows a mic at 0 degrees.
Generally, 0 degrees is used for a stereo setup.
90 degrees, i.e. Vertical or pointing to the ceiling, is used for a surround setup.
I’m sure I tested both, some years ago now, and decided that in my room, any difference was insignificant. As I’m sure you’ll appreciate it is a simple test for you to perform and come to your own conclusions.
You may like to read this excellent topic guide-how-to-do-room-correction-and-use-it-in-roon
It suggests measurements can be performed with a moving mic rather than sticking to a static/fixed position.