Z6II vs Z7 vs Z7II

[A7-BAJ]

Hey lads,
Hope all is well. I currently shoot with a Nikon D750 + Nikon 200-500mm F5.6 / Tamron 70-200 F2.8 II

Was hoping to upgrade at some point to mirrorless. Looking online, a gently used Z7 and Z6II go for about 1250 here, while Z7IIs go closer to 1900.

My Questions:

1. In practicality, what are the main differences between the Z7 and Z7II, and is the Z7II really worth the extra $650?
2. How does the Z7 preform for aviation specifically, with the lower buffer?
3. Is the D850 still a strong body? At the same price point, does the D850 still have any advantages over the Z7/Z72?
4. How does the Z6II stack against the Z7/Z7II despite the lower pixel count? Is it a significant step up in quality from the D750, and at the same price point is it more worth than the Z7?

Thanks!

[Defacult]

1. Mostly QOL upgrades like qual card slot and better autofocus, if you have plenty of budget feel free to buy the Z72, if not the Z7 should be pretty similar
2. Z7 is made as a high resolution camera in mind for landscape, which also means if you like to crop a lot or like your details, it's very good.
3. D850 is mostly worse than the Z72 apart from build quality, the D850 is a tank but the Z72 is no plastic toy either. Still, the D850 is very capable and definitely won't be holding anyone back.
4. AFAIK it should have slightly better auto focus (I may be wrong). High ISO will be better. But also a lot less room to crop and relatively less detail compared to the Z7/Z72. It is also cheaper.