There are no surprises regarding the original Nikon flashes I have, the SB-700 and the SB-900, both of them work as described in the manual of the Z7. What I need to see is how well the cloned products behave on the Z7, and here I found out a few surprises.
The image to the left was used as reference image to test the exposure to see if iTTL works as it supposed to be.
All the pictures are all clickable if you want to see a larger image.
The Nikon SB-700 and SB900
As said before, both of them work individually, or in any combination just as described in the manual of the camera. The only thing that is not working is the AF assist LED, but this is known and is as expected.
It seems also that the SB-700 and the SB-900 together with the Yongnuo YN622N kit seems to work well in all modes, iTTL and manual, single or dual flash, compensation and so on. Once again, the only thing not working is the AF assist LED which is built in the Yongnuo YN622N kit units, but again, this is as expected.
The EXIF of the image always shows that the SB-900 is used, even with the YN622N-TX.
How to fool the camera
Of course, in all cases when the YN622N is used, the flash information in the EXIF still claims that it is an SB-900, regardless which flash it is triggering. This doesn't really matter as long as it works in iTTL mode.
My older flashes are all made for film cameras, and they work just like they worked on my old film cameras.