I am sad to report that I decided to return the Z7 and replace it with a D850.
The thing that sold me on moving from Canon to Nikon was the killer AF acquisition, lock, & retention of D500. I had originally planned on the getting myself a D500 & D850. When I was at the counter gathering my new gear, they slid the Z7 in front of me and I began to consider it. I asked about the focus engine & things like Group AF mode and the ability of the Z series to quickly lock & hold focus on wildlife. Being such a new camera, they did not know all the ins & outs of the Z7 and assured me it would be "at least as good" as the D500.
Fast forward a couple trips to various parks & refuges, and I had somewhat of a different experience than expected.
I have to say that there are many things about the Z7 that I REALLY like (EVF, Histogram in the EVF, instant image review in the EVF w/o ever pulling your eye away, "real time" visual reference to exposure changes, and UBER SHARP images of static and/or slow moving objects).
For me, the issue has to do with with the very thing I asked about initially - the AF system as it would apply to a wildlife photographer. It does not have the AF modes I expected and is not quite on the same level as D500, D850, D5 in that regard. Additionally, the buffer fills too fast so something as simple as trying to follow a bird launching from a perch can be an issue.
For me, at this point, the D850 is a better option.
There is certainly a greater than zero chance I could get one again, only for different reasons with different expectations.
I pass the torch on this thread to whomever would like to carry it on.