With prices for used PC laptops falling like they do, I wouldnt buy a brand new machine. Realistically even a year old used machine will be so much cheaper and as far as I am aware there have been no major breakthroughs in CPU and GPU in the last year.
GTX 1070 is enough in my opinion. It can run a Vive comfortably with even the latest Steam games at totally smooth fps. I would assume that for vvvv even for VR you need a lot less unless you have some magic shaders that are super demanding. Even with Superphong + Depth of Field at 8xAA I get a nice 45 frames/s at 1080p on a GTX1070 - although this is in no way objective, since it depends on so many more factors, but I am not sure how much faster the 1080 would be. There are however quite a few more laptop options once you go "down" to a 1070 or even 1060.
So rather than going for the latest and greatest, I would go for a solid performer from last year and save some money to invest in other goodies.
Also dont forget external GPUs! With Thunderbolt 3 and USB-C finally becoming somewhat common even outside of Apple, this is really a great option if you need lots of (upgradeable!) graphics power, so keep this in mind. Most times you need a lot of graphics power for vvvv is not in a totally mobile environment, but somewhat stationary, like hooked up to a TV, projector, vive/rift, etc. Not to mention power. These ultra-performance laptops usually have atrocious battery-life when running graphics-intense stuff.
So, not really making any recommendations, but just some food for thought.
Let us know what you decided on in the end and how it all panned out.