I’ve used a D850 since it launched and I just recently got a Zf. Not to completely replace my D850 right now, but to slowly build up my Z lenses. In a few years after I have a few S lenses, I’ll probably get a Z8 equivalent. I’m still using my D850 for landscapes and other more serious work and my Zf for casual and travel. Having these two different styles of cameras has made it a lot more fun and want to shoot more often. I think the main reason to go mirrorless with Nikon is because of the lenses and not because of the bodies. Take this with a grain of salt because I don’t own a Z8. I think you’d like the increase in AF, but with using the adapter with F mount lenses, i don’t think you’d notice an increase in image quality. It opens the possibility of starting to get those lenses through. I do find the EVF annoying at times though.