I have a Z7 (not so patiently waiting for a Z8 - come on! lol)
Of the bodies I've tried across the manufacturers, and note I have not shot with a Z9, I like the Z7 EVFs natural view the most, and I dislike the Fuji GFX (medium format) and Panasonic EVF the strongest. Canons are pretty good, Sonys are "okay". Even though at the end of the day I prefer an OVF, I've found I've adapted quite quickly to the EVF of the Z7 for most things (which honestly surprised me) and now can shoot just as well switching between that and my D850 without nary a thought to the viewfinder if things are static (see next sentence lol)
However, the Z7 EVF is still laggy - it needs refresh rate improvement, so if you switch views/scenes quickly, it tires the eye a bit. It's not a body I would care to use to follow things that move (and honestly, the AF is not that great at such, so it's not the body I would use for that anyway).
I expect the next gen Z body will have the refresh rate improvements; maybe the Z9 is "it", haven't shot that one yet.