Some test results...
SlashCam have the S1R II 8K at 22ms, but I think open gate brings that closer to 30ms?
Sony a1 is at 15ms for 8K, no crop.
The 4K/120p is also much better / cleaner on the a1:
S1R II
https://www.slashcam.de/artikel/Test/Panasonic-LUMIX-S1R-II-Sensor-Bildqualitaet---Debayering--Rolling-Shutter-und-Dynamik--Rolling-Shutter---Panaso.html#RollingShutterPanason
This is important because 4K/120p is usually what sets apart your £3k new camera from a £1k used S1H.
Granted there's a few new features that have come through since.
But if you don't need the speed, the a1, S1R II, Z8 and so on seem a bit pointless to me?
There's so many cheaper options if 60p or even 30p is your only need.
a7 IV, S1H, Fuji X-H2, and so on.