I use a jogger buggy with 20 inch rear wheels works well in rough terrain. it's what someone would push a child in when running. I carry two camera backpacks one with a Nikon D500 with vertical grip and Tamron 150-600 G2. The other a Nikon D850 with a vertical grip various lenses up to Nikon 80-400 2nd version. Plus folding chair, monopod, lunch, water, jacket. No weight on my back while hiking around. Works great as long as the trail is wide enough which most are. I'm in Colorado so up and down hills. Down can get a little tricky sometimes. Mine has a hand brake which helps to keep it under control.
Keep the bags unzipped for quick access.

I use a jogger buggy with 20 inch rear wheels works well in rough terrain. it's what someone would push a child in when running. I carry two camera backpacks one with a Nikon D500 with vertical grip and Tamron 150-600 G2. The other a Nikon D850 with a vertical grip various lenses up to Nikon 80-400 2nd version. Plus folding chair, monopod, lunch, water, jacket. No weight on my back while hiking around. Works great as long as the trail is wide enough which most are. I'm in Colorado so up and down hills. Down can get a little tricky sometimes. Mine has a hand brake which helps to keep it under control.

I have a Nikon D500 with grip and a Tamron 150-600 G2 and use a Thinktank glass limo backpack which has room for the camera, lens, and hood all attached. I'm 72 and carry the camera by large tripod foot on the lens. Shoot mostly handheld. The backpack works well.

I am using the new version of Nikon 80-400 and a Tamron 150-600 G2 on a D500 with mostly great results from both lenses. The Tamron is not great in low light however.

I have a Nikon D2x bad low light performance, currently using a D500 I have Nikon 17-55 f2.8 lens which greatly improves low light performance in the crop sensor cameras. Expensive new but reasonable on ebay. For longer 2.8 zooms be prepared to spend a little money. I also have a D3 and a D750 full frames with pretty good low light performance with slower lenses. Depending on the lenses you currently have could be less costly to get a D750 or D780 but you'll lose the crop factor. Keep the D7500 and consider the D750 or D780.

I use a jogger buggy like the ones people push their kids around in. 20 inch rear wheels is ideal for fairly rugged hiking trails. Wheel width is a limitation on really narrow trails. I typically carry a D500 w/ Tamron 150-600 G2 and a D750 both cameras w/ vertical grip in their bags. monopod or tripod, small folding chair, water, lunch, extra jacket, etc. Works great no weight on my back. I can walk for miles without much difficulty.

For hiking, bird hunting, wildlife, etc. I use a jogger buggy made for pushing your kid around with the larger rear wheels for rougher terrain. It's limited for really narrow trails otherwise works great. I carry one bag with Nikon D500 w/vertical grip and Tamron 150-600 G2, up to two other camera bags, up to two folding chairs, monopod, extra coat if needed, water and lunch. Works great no weight on my back and seems to work as a walking aid. I've spent many ours with it on the trail. Low impact on the surroundings. I live in Colorado and have it many places where the access is wide enough.

I have Thinktank glass limo it holds my Nikon D500 with vertical grip and Tamron 150-600 G2 with the hood attached. Plus a little room for accessories.