And oh yes - leave your flash at home.

I regularly go to Botswana & Namibia. Expect wide open spaces and wild life - both near and far.
Also consider that all that gear need to be carried and kept safe somewhere.

I find that the following works fine on my D750 ( with a D7500 as spare) -

For Wild life & Birds : 150 - 600 Sigma lens, 1.4 teleconverter, 100 -400 sigma lens. Some sort of support ( eg bean bag or similar)
All the rest - 24-120 mm and maybe a 105 macro for the small stuff.
Tripod & wide angle lens helps but only if you are into astrophotography - which is great in the Kalahari. But that is a lot of weight to carry for limited use.

I had a similar issue with my Sigma 150-600 C - it simply focused all over the show with my D750. The Sigma dock allows you to finetune the lens at around 5 -10 different settings ( Focal lenght and distance - eg 150mm at 5m, 10m, 20m etc and then at the same thing at 200mm etc etc. )

That sorted the lens it self. Then I also set it on my bodies ( D750 & D7500) as well. The bodies only allow to set for front & back focus on any focal length. Minor adj was required on the 2 bodies.

Now it is tack sharp.

The Nikon body stores the settings by lens.

I did not have similar issues with my Sigma 100-400 but I guess the same principle will apply.