On the D750, with the above settings, the camera will continually focus as long at the back button is pressed in. For the reason you noted, I found that VERY helpful, as I hate having to go into menus, especially if I’m in a hurry. My mind “locks up” under pressure. 
Joanna, can you please take a photo of your menu settings? I think they are different than on the D750.
I just hope my mind can remember that I’ve put it on the “my menu” on the fn2 button 
Do you realise this old dog has just learnt yet another new trick?
Oops, I thought this was mostly a one way street, you talk, we listen!
Well, what is “clear” and what is “easy to focus” are subjective terms that are hard (impossible?) to quantify. But no question, the lower the light, the harder it is to see clearly and to focus accurately with either optical or EVF. My Canon R5 has no trouble with low light that used to give me fits with my DSLRs.
I don’t know about, say, shooting star trails or long time exposures because I don’t do them. But other people do and their photos are all over the internet. FStoppers has an incredible assortment of photos from all over the world in their photos area, and most of the work here was shot with mirrorless. Most of the photos are “artistic” and many of them were shot in very low light.
No, I’d like to see the menu for all the focus options, a1, a2, a3, like this:
I’m curious if you have the same setting for a8, the one that @Wolfgang wrote about. I don’t know if the D850 has a similar option.
that is possible but you can have both.
and i have a fn button set up as lock unlock touchscreen because i am also a lefty and my nose is randomly rearranging focuspoints, aiming centre and oops, focused on right bottom side… 
one tiny issue, every time i forget which button it is i programmed to do so…
i still need to make a cheatsheet of some of the settings and custom setting savings for a purpose.
( 
christmas holiday in lockdown? time to be lazy or time to do things …)
Yes - no matter what I do with the shutter release, the camera does not focus. What I saw as I was pressing the release is what will be captured.
My D750 will only focus if I press the button on the rear of the camera. For a better understanding of this, watch the video I posted - there’s more to it than I can explain - his explanation is much more thorough, along with his reasons for doing it this way.
Your D850 may or may not be as easy to program this way as the D750. Again, watch the video - and you might enjoy watching the full video, as he offers lots of other suggestions, almost all of which I then did on my camera (other than video, which I haven’t been doing on the D750 - yet).
The D750 and D850 have a different button layout and menu structure. While Nikon keeps a lot of the menu entries similar, they are not (necessarily) labeled the same, which also can have changed with firmware.
– When I remember my former D800, there was a quite a difference in how to configure AF.
The reason I will never get the Fuji X100v is because they went to a touch screen. I have enough to deal with using menus and buttons. I hate it when unexpected things happen to any device simply because I touched the screen.
Does the D850 have a touch-screen? My first move if I bought one would be to permanently disable it. Thinking about what you wrote sounds like a giant headache to me. And if it’s not possible to disable the touch-screen, I doubt I would ever own one.
If the new Z cameras use touch screens, that’s one more reason I would avoid them.
My g80 setup modes:
found it again : i have centre button in apeturewheel set up a on/off touch screen. 
and if i forget i can see in cameramenu fn button setting which would do which…
and change them if i like. (14 different things of each button to choose from)
i have 11 buttons and 5 are touchcreen buttons
works quite well.
edit:
ps fn4 i never used it but i can “test” effects of shutterspeed and aperture…
a “previewmodes”… now i know why: it’s like taking a test picture without storing it. shutter range : 8sec-1/16000e…
geesh an other task this holiday: redefining function buttons and custom cn0 cn1-1 cn1-2 cn1-3.
reading time 
Does the D850 have a touch-screen?
check → Nikon D850 Review
Yes but it’s one of the first things I disabled 
More about this also here from Steve Perry
Wow!!! This just unlocked a whole load of mystique behind all those different AF modes that I never quite got the hang of. Especially when I also looked at some of his videos on the subject.
You do realise I’m now going to have to take time out to try some of this stuff in between my regular work? Anyone got a spare 25 hour day to hand?
Here are two screenshots that show all the Autofocus options on the D850…
Sometimes I wonder about simply trying to remember to use manual focus but my eyes aren’t what they used to be and, without my trusty 7x loupe for the ground glass screen on my 5" x 4", trying to pick what is sharp isn’t always easy. Unless I switch to Live View and use the Focus Peaking indicators to help me.
One of the neat features of the Canon R5 (mirrorless) is that you can have it magnify the area that you are focusing on and then manually tweak the focus.
In fact, for almost any mirrorless these days, including Nikon Z. Mirrorless does have a number of benefits…
some of my D750 presets
Two quick thoughts.
First, my Leica M is a rangefinder camera, not a DSLR. It has “live view” on the rear screen, that essentially makes it “mirrorless”. If I’m looking through the Visoflex accessory, the camera knows I’m focusing, and shows an enlarged view in the Visoflex, complete with focusing aids.
Next thought, Perhaps Nikon could sell their version of a Visoflex, that would mount on top of a Nikon DSLR, and then the camera could provide both an optical viewfinder and a “live view” as Leica does?
I’m sort of stuck. I can see a lot of advantages in a mirrorless camera over a DSLR, but the whole idea of the viewfinder is to show the scene I am photographing as well as possible. For the types of photos we’re discussing here, that puts Joanna’s Nikon D850 ahead of a Nikon Z9. (For sports photography, or bird photography, or action photography, I guess I would need to re-consider.)
The more I read, the less I’m interested in a Nikon Z, but I still want to see one for myself.
