I think you’re over thinking it. The z5, z6, Z6ii, and Zf are all amazing cameras. If you were the kind of person the minute improvements or differences actually mattered, you wouldn’t be wrestling with the decision or posting. Pick the one that’s the most comfortable, you’ll use it the most.

The low light on all of them are great, and you can push the iso to absurdly high limits and get gorgeous results. Especially if you run through Lightroom denoise in post. The Zf looks cool if that’s your thing. The z5, z6, Z6ii are the same physical size and have the same superior ergonomics. I just shot a wedding in a dark bar with a z5. And also an ancient d700. Both were great. Frankly I think the non Zf look cool too.

Didn’t know there was a non scary brain hemorrhage. Learn something everyday. Be well.

My 2 cents, get a z5 and a couple lenses. It’ll blow you away coming from d5xxx. Only get the others if you shoot sports.

Also, before you start talking video specs, z5 shoots non cropped video at 1080, cropped at 4k. I had a serious videographer tell me even he can’t tell the difference between 1080 and 4k. I believe him, but I’m not video centric.

24-120/4 if you can afford it. 24-70/4 is pretty sweet too. And cheap on eBay. The 40/2 will not come off your camera very often if you get it.