D850 to Z7 here. It's nice to have choices. As one who is backpacking and lugging the stuff around, I am delighted at the 1+ pound I shed going to the Z7. Smaller, lighter, IBIS, a great advance.
Startup time in landscape is not an issue. It is noticeable, but I just turn the camera on as I swing it up to my eye. My only "dislike" was a moment in the Zion backcountry when it was so beautiful that I shot for several minutes straight. When I took my eye from the EVF I had a moment of vertigo. Luckily I wasn't standing on a ledge or cliff.
I do find the sensor a little noisier than the D850, but the IBIS lets me hand hold longer at base iso to avoid that.
Textured button? I forgot about it immediately. Don't use it and don't notice it.