I am aware of how small the Fuji f2.0 primes are - as Armand says, the differences decrease when you're using zooms.
I always use zooms to avoid changing lenses frequently on the trail, and that makes it closer. Another thing to consider is that in order to have any image stabilization at all (which I consider essential on the trail - tripods are darned heavy), you aren't taking advantage of the weight reduction of both the X-T2 and a prime lens - that combination is unstabilized unless the prime is the large, heavy 80mm Macro or the upcoming huge, heavy 200mm f2.0 - not Fuji's fault, 200mm f2 lenses are heavy due to physics! You either have to use a zoom or the X-H1 body to gain stabilization. Some of the primes are also non weather sealed - that varies by the lens.
The Z7 body is comparable to the X-H1 in size and weight comparing stabilized bodies (the Nikon is actually slightly lighter when you consider that it contains the equivalent of two Fuji batteries, and, while its CIPA reports are disappointing, real world tests are seeming to show that it gets 1.5 to 2 Fuji batteries worth of performance) The Nikkor 24-70 falls in between two Fuji normal zooms in size - there is the little 18-55 f2.8-4 , which is a great little lens (best kit lens on the market for years), but it isn't as good as initial reports show the Nikkor 24-70 will be. The other option is the 16-55 f2.8, which is a fantastic lens (probably comparable to the Nikkor), but significantly heavier than the Nikkor (and it's Fuji's one and only unstabilized zoom - why did they do that?). It requires the X-H1 for stabilization... The Nikkor 14-30 will probably be comparable to the Fuji 10-24 in size and weight.
You can get a wide variety of results out of camerasize, depending on exactly what you choose for options. Those tiny Fuji primes on the smaller bodies (and, even more so, a small Micro 4/3 body with a pancake) allow for some very small systems. For a weather sealed kit with top-quality normal and (admittedly upcoming for Nikon) wide zooms and stabilization in either the body or lens, the differences are minimal.