On my Z6:
F2 is 100% zoom. I use this a lot. It zooms to the focus point in the frame, then another F2 press zooms it all the way out. That's faster and way more efficient than repeated pressing of the "+" and "-" zoom buttons.
I can override the AF with the lens focus ring, and see the zone of focus move in and out.
100% zoom also works great on Image Review, zooming to the focus point.
F1 is usually (the default for F1?) metering mode.
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I normally shoot "landscape" type scenes, in AF-S, usually single point AF.
For subject tracking, I use U3 settings. So it's just two clicks of the Mode dial from Aperture priority to U3. I can switch while looking through the viewfinder.
I really like U3 for Subject and face tracking -- now it's an instant switch to tracking, no menu choices needed. And it reverts back to my Aperture settings when I change back to Aperture.
Switching to U3: When I press AF-On, I get the dancing red focus boxes, with the camera looking for focus points to select. If it sees faces or eyes, it auto switches to face/eye tracking. Note: this face/eye that's tracking won't be focused unless I press AF-On or half press shutter.
If I press F1, I get the centered white box. Hold the AF-On (or half press shutter) and it continuously tracks and focuses whatever was in the white box, following it all over the frame. Press F1 again to revert.
My settings for U3:
a4-face eye detect ON,
f2-Custom Controls-->Fn1: Subject Tracking.
Also AF-C and Auto-area AF. All these changes revert back to my usual settings when I'm out of U3.