You can read my blog post that Rob refers to here: Top birds in flight settings for Sony a9II
Hey Rob,
Absolutely, yes! I set my desired aperture and target shutter speed in manual mode and then use whatever ISO that I need to get there. There are many examples in this blog of images made using a higher ISO than the 1,600 that you limit yourself to.
UNCOMPRESSED RAW AT HIGHER ISO
One consideration when photographing action at high ISO with a Sony a9 or a9II is to consider lowering your capture rate and switching to uncompressed raw images to lower the noise in the dark portions of the image. I usually switch to uncompressed raw at 6,400 ISO.