I love wildlife photography. Photography is not my profession but i like to give voice to the voiceless mainly through pictures.
I love Bigcats. I also do click birds if chances arise, wouldn't like to miss them. But bigcats are a priority.
I spent maximum 1-2 months in a year in the jungles, rest i have to work. So, i don't want to miss any chances because of less reach, or angle of view.

I am confused between the D750 and D500. The D850 is out of budget. The other Dxx series is not at all available here or older ones like D3s.

The bigcats are mainly active in early morning and late evening especially the tigers, which i shoot mostly as they are in India.
But these leads to low light scenarios.

I currently own the D3400 with 18-55mm & 70-300mm VR kit lenses which is good upto 2000 ISO & have used D7100(rented) which was good till ISO 3200 max. But picture quality takes a hit after 1600 ISO in both.

I have recently got an used Nikon 70-200mm VR II f2.8 for 785 USD and an used Nikon 200-500mm f/5.6 for 642 USD.

I know the D500 have all the fancy features of D5 and D750 have nothing of those features, even a max of 15 raw bursts buffer. But it has low light performance which helps with shutter speed when handholding. There is no room for tripods or monopods in shared vehicles. I will be attaching a few images with focal lengths if possible, you can check them.

Price of D500- 1614 USD ( Also have noticed a grain present in D500 shots, in sunlight for birds its not noticeable but in shades for mammals i can see it in few images)

Price of D750- 1271 USD, used around 930 USD
Price of D7200- 700 USD, used around 400 USD

So, i could get a used D7200 and a new D750 for the price of a new D500.

You maybe a bit wrong there. Most of the reviewers say, the D500 has excellent low noise performance considering its a DX sensor. And the last part "considering its a DX sensor is a twist".
I have also seen some recommending D500 and themselves using D810, D5 and D750 for their photos.
When comparing any DX body to D500, its a no brainer but when comparing it to a FX it gets tight specially in lowlight. In earlier days nobody had 153 focus points and 200 raw buffer, but still they made good images of birds.

I love wildlife photography. Photography is not my profession but i like to give voice to the voiceless mainly through pictures.
I love Bigcats. I also do click birds if chances arise, wouldn't like to miss them. But bigcats are a priority.
I spent maximum 1-2 months in a year in the jungles, rest i have to work. So, i don't want to miss any chances because of less reach, or angle of view.

I am confused between the D750 and D500. The D850 is out of budget. The other Dxx series is not at all available here or older ones like D3s.

The bigcats are mainly active in early morning and late evening especially the tigers, which i shoot mostly as they are in India.
But these leads to low light scenarios.

I currently own the D3400 with 18-55mm & 70-300mm VR kit lenses which is good upto 2000 ISO & have used D7100(rented) which was good till ISO 3200 max. But picture quality takes a hit after 1600 ISO in both.

I have recently got an used Nikon 70-200mm VR II f2.8 for 785 USD and an used Nikon 200-500mm f/5.6 for 642 USD.

I know the D500 have all the fancy features of D5 and D750 have nothing of those features, even a max of 15 raw bursts buffer. But it has low light performance which helps with shutter speed when handholding. There is no room for tripods or monopods in shared vehicles. I will be attaching a few images with focal lengths if possible, you can check them.

Price of D500- 1614 USD ( Also have noticed a grain present in D500 shots, in sunlight for birds its not noticeable but in shades for mammals i can see it in few images)

Price of D750- 1271 USD, used around 930 USD
Price of D7200- 700 USD, used around 400 USD

So, i could get a used D7200 and a new D750 for the price of a new D500.

I love wildlife photography. Photography is not my profession but i like to give voice to the voiceless mainly through pictures.
I love Bigcats. I also do click birds if chances arise, wouldn't like to miss them. But bigcats are a priority.
I spent maximum 1-2 months in a year in the jungles, rest i have to work. So, i don't want to miss any chances because of less reach, or angle of view.

I am confused between the D750 and D500. The D850 is out of budget. The other Dxx series is not at all available here or older ones like D3s.

The bigcats are mainly active in early morning and late evening especially the tigers, which i shoot mostly as they are in India.
But these leads to low light scenarios.

I currently own the D3400 with 18-55mm & 70-300mm VR kit lenses which is good upto 2000 ISO & have used D7100(rented) which was good till ISO 3200 max. But picture quality takes a hit after 1600 ISO in both.

I have recently got an used Nikon 70-200mm VR II f2.8 for 785 USD and an used Nikon 200-500mm f/5.6 for 642 USD.

I know the D500 have all the fancy features of D5 and D750 have nothing of those features, even a max of 15 raw bursts buffer. But it has low light performance which helps with shutter speed when handholding. There is no room for tripods or monopods in shared vehicles. I will be attaching a few images with focal lengths if possible, you can check them.

Price of D500- 1614 USD ( Also have noticed a grain present in D500 shots, in sunlight for birds its not noticeable but in shades for mammals i can see it in few images)

Price of D750- 1271 USD, used around 930 USD
Price of D7200- 700 USD, used around 400 USD

So, i could get a used D7200 and a new D750 for the price of a new D500.

My primary cameras are a D810 and a D850. A few months ago, I got a D500 for those occasions when I wanted excellent results, but wanted smaller files than those produced by the 850/810. I find that the D500 produces images equivalent to the 8XXs, apart from the difference in overall resolution. (I also have a D300s, mentioned above. I loved it when it replaced my D200, but it cannot in any way come close to what the newer cameras can do, especially low light.)

I do a lot of low light photography, including night sky photography. The D500 is not my primary camera for night sky because of wide angle limitations imposed by the smaller sensor. I have never encountered any meaningful low light limitations with it that cannot be overcome with good technique, despite hearing comments similar to yours in the past. It has always been essent9ially equivalent to both D8XXs in every important way.

In response to your specific noted concern, the D500 does have an internal focus motor. In fact, it is the most compatible of any Nikon with both older and newest lenses.

Please note that I do not emphasize photographing wildlife, but from my understanding of and experience with the D500, I do not see any reason that it should not be a good choice when coupled with appropriate lenses. And it will not cost $1000 to add a grip. Yes, a new one is about $400 US, but you do not need the big battery. Used Nikon grips are about $200. I cannot recommend any 3rd party grips. All seem to have some performance limitations.

I use the D500 with the 200-500 Nikon and get great shots. In focus and sharp. The D500 also shoots at 10 fps. much faster than the D7200 and D750.
In addition, one of the best focusing modes is called GROUP AUTO FOCUS, the D500 has it, the other two don't.
In addition, the D500 shares a second focusing system that both the D850 and D5 have.
In short, if you want to shoot wildlife, the D500 is the way to go. Don't forget the 200-500 which, by the way, has an electronic diaphragm which gives you exacting exposures at 10 fps. Third party glass does not have this.
Good luck and keep on shooting until the end.