will the picture quality differ if i use canon's 7d mark 2 instead of 760d?

No. What's making the 7D Mark II so much more expensive is faster and more accurate focusing system; it's got a much faster shooting rate of 10 fps vs "just" 6 fps on the 760D. Now while this may not seem to some to be too much of difference, you need to also consider the fact that the 760D will drop to about 3-4 fps once it's in continuous focusing mode. What is also adding to the cost of the 7D Mark II is it's internal buffer. You can shoot about 31 RAW images with the 7D Mark II at 10 fps before the buffer fills and the camera drops to just 1 fps. With the 760D (T6S for us folks in the US), the buffer can only hold 6 RAW images before the frame rate drops to just 1 fps. That's a massive difference for anyone shooting sports or wildlife.

With the 760D, the focusing system can focus down to f/5.6 meaning that the maximum f/stop required for it to focus is f/5.6. If you put a 2x teleconverter onto a 70-300 f/4-5.6 which effectively makes it a 140-600 f/8-11 lens, the camera won't be able to focus the lens. The 7D Mark II has the ability to focus down to f/8, again giving the user the ability to get the shots with various lens/converter combinations. Plus, when just using a lens alone, such as a 50mm f/1.8, the 7D's superior f/8 focusing system will allow it to focus better in much lower light levels than the 760D.

So while the image quality of these two cameras aren't any different when taking simple photos that both can easily handle, the 7D Mark II going to produce better photo quality, provide you with the ability to actually get the shot, and get it consistently. That's where your money is going, plus the 7D Mark II is far better built and weather/dust proof while the 760D is not.

You can compare ISO performance of these cameras here: https://www.dpreview.com/reviews/image-comparison?...

As you can see there are pretty much the same.

You can compare features of each here: https://www.dpreview.com/products/compare/side-by-...

No.

But if you can afford that price difference, shooting will be a whole lot of fun with the better camera.