Thanks all, appreciate the various input from everyone.
I downloaded a RAW for the A7C ii and at base ISO it is showing that strange noise that my A9 did in certain areas. A RAW from the Z6 iii doesn't seem to have this in a similar area, although I'll admit my brief test may not be accurate nor comprehensive so I'm still open minded about this. Photos are at the end.
I do remember with my A9 that I often switched to electronic shutter to overcome the mechanical shutter's 1/8000 when using my 1.4 lens in sunlight and the A7C ii's electronic shutter only goes to that. But I doubt I'll get a 1.4 lens for this setup because the size factor gets ruined, so perhaps a moot point.
I see that the A7V also has a partially stacked sensor (and a mechanical shutter) yet achieves much higher dynamic range than the Z6 iii. I've done some brief skimming and is it to do with the Dual Gain Output tech of the A7V being applicable from base ISO, hereas the Z6 iii has more of a conversion type DGO which comes into play at ISO 800? Or have I got that totally wrong... lol
That A7V does look like the complete package, but I'd need to look at the size. Even the size of the Z6 iii is now making me wonder if my primary goal of a smaller system is being compromised. I'm keepin the D810 for specific landscape panos, which has excellent dynamic range, so perhaps I shouldn't be so concerned with the DR of the CSC I get? I do like Nikon colours though, although does that really matter so much if using RAW?
This is turning into a bit of a minefield for me.
Here's the photos I was talking about, the first two are the A7C ii and have that noise at base ISO. The last one is the Z6 iii which doesn't seem to be as bad. I tried to get similar areas of lighhting to demonstrate it,
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