Out of the three cameras, I only own the D850. Focus tracking is outstanding. The high pixel count allows for significant cropping to "extend" the reach of your lenses. Focus performance in the live view mode is dismal, so you'll have to use the viewfinder with the mirror down, and that means quite a bit of noise if you're taking burst shots. The Z50 will be lighter and quieter and will already have the effect of cropping your FX lenses to extend their reach. You should use the mechanical shutter at high shutter speeds to avoid the rolling shutter effect on moving subjects. None of these cameras are high ISO champions, but you should be able to get by. Assuming you are in the stands, maybe forget the wide angle zoom. I can't thing of anything more at the moment. I'm sure others will contribute their thoughts.