>>3253960I use manual ISO in a number of conditions, such as when I'm using the flash, or in sunny conditions, or when I'm using a tripod.
Also, even though the X-T2 and X-H1 have a way to match the auto ISO steps to 1/focal length shutter speeds, on the X-T1, it's not quite as advanced, so you do need to take control manually sometimes.
You do get pretty good detail in the high ISO range (pic related is from a processing comparison, but is still a good example of sharpness at ISO 1000), but details (also dynamic range) would always be best at base ISO. So landscapes, macro and other types of photography where you want to preserve details or make the most out of a single photo's dynamic range will look best at ISO 200. Above 3200, you really lose the fine details, at least on the X-T1.