I guess I am one of those photographers that just can not stick with one camera brand. I use both Sony and Nikon systems depending on my photographic situation. 

That A9iii just has such an amazing focus speed and reliability. I love it. Especially when paired with fast lenses. Since I just love the higher megapixel count, I now use the Sony A1 2. That too, is amazing.

A few years back I purchased the Sony A1 and the FE 200-600mm F5.6-6.3 G OSS lens. I found that the Sony cameras did an excellent job at animal eye tracking. Even if the animal eye tracking did not pick up the subject's eye, the User could assign a tracking feature to a camera function button. Viola! So many more keepers, as the tracking is awesome even for low contrast and fast moving subjects. 

Furthermore, the Sony cameras allow the User to customize the camera allowing the User to "create" a camera to suit his/her own personal photographic needs. Just dig into the menus and see. 

I loved the Sony A1 so much for action and fast moving subjects that I purchased the FE 100-400mm F4.5-5.6 GM OSS lens, the FE 70-200mm F2.8 GM OSS II G lens and the 300mm! And that is now my favorite lens!

And now to Nikon. I also use the Nikon Z9 with Nikkor Z 100-400mm F4.5-F5.6/VR S. This setup is great for long treks in the mountains when you need something rugged for the changing weather. I also use the 800mm PF, which is light yet sturdy.

Since Nikon has produced some amazing glass over the years, I have a small collection of amazing lenses that work excellent with the FTZ II adapter. There is no degradation in the focus speed or the image quality. And depending on my needs, again, I may use the AF-S Nikkor 500mm F4E FL ED VR, AF-S Nikkor 500mm F5.6E PF ED VR, AF-S Nikkor 180-400mm F4E TC1.4 FL ED VR ( I love this lens because of it's range and the built in teleconverter), or the Nikkor AF-S 24-70mm F2.8E ED VR. 

And how do I carry my gear? I use different camera backpacks depending on the amount of gear I need to travel with. For lighter loads, I like the Gitzo Adventury 30L Camera Backpack. Plenty of room for gear, water and extra clothing. When I need to carry a larger load, I prefer the Mindshift FirstLight 40L which can carry two camera bodies and large lenses with room to spare. 

And I always pack my Garmin In Reach, a compass, whistle, extra water and clothing for those potential mishaps.