What do you have sharpening set to in LR? [open up a RAW file in LR and check this] Adobe have the default for Fuji cams at 40, this is way too high - it is the first thing I do when I load files from a new Fuji camera into LR - reduce the default sharpening to zero! and only apply it when needed - and on top of this I use mask sharpening. Part of the issue is that with over sharpening, any noise especially at higher ISO levels, gets greatly exaggerated. Try this for a start. I am comfortable shooting up to 6400 with the X-H1. Though the older sensor has actually been proven to be slightly better than the newer one - though the newer T3 sensor holds better sharpness at higher levels. Hence the need to drastically reduce default sharpening for the T3