LOL,Bioshock Infinite runs fine on a FX6300 with a GTX660,so I think it must be some issue on the driver side with your SLI GTX1080TI.
I even tried it on a A6 3670K and an HD5850 and it ran!!
Remember,ROTR??
Plus even though a Core i7 7700K that would be the best CPU for FO4,which I do play,at £300+ its a waste of money,as I tend to keep my platforms for at least 3 to 4 years,which I would argue is what many people do. Sure forum enthusiasts will upgrade every year or two,but that is not really practical for most people!
I upgraded to SB when it first game out with a Core i3 2100,so that is how long I have been on socket 1155 - so my only chance of ever getting SKL/KL is if the CPU and mb was relatively cheap.
What is the likelihood once Coffee Lake is out all the Core i7 7700K and more importantly the Core i5 7600K benchmarks will be dropped within a year just like all those pesky GTX1060 3GB ones??
Edit!!
Thats quite an intensive part too. One GTX1080TI at 4K though.
Plus if you are really that worried about getting Intel only,then you should be waiting for Coffee Lake,and especially when the Z390 motherboards are released at the end of the year.
6C/12T at a similar price to a Core i7 7700K with similar single core performance - that sounds like a decent combination there!
Second Edit!!
Even Nvidia are now recommending Ryzen and Threadripper:
https://www.pcgamesn.com/nvidia/nvidia-battlebox-pc
https://www.geforce.co.uk/hardware/10series/battlebox/
On one of the Nvidia webpages they even did a Ryzen build IIRC.
So methinks,that if that is the case Nvidia will be working on those optimisations over the next few months which is good news for AMD!!