I don't understand at all why your histogram is not changing with exposure - it does on my cameras. There is something wrong. The little histogram that you can have in the corner of the viewfinder is of little value - it's too small. If, like on my x-t5, you can have a full histogram with all three colour channels showing, assign a button to it. The resulting histogram is accurate for the jpeg only. The right hand highlight end is fairly accurate for raw, although you may squeeze out another half stop. You cannot recover blown highlights, so make sure the right hand side is not bunched up against the limit. Also remember, that if there are specular highlights in the picture, such as sun on water or mettalic surfaces the highlight end will show a narrow peak, which in this case, will be OK. For raw you can pretty much ignore the shadow clipping as the shadows will be recoverable, unless they are really dark. The histogram is of great use when taking landscapes with a tripod. I use it frequently. It tells me when I need a separate exposure or grad filter for the sky. Of course, you wouldn't use it for street!