Sorry if this is considered derailing, but I thought it was relevant to the discussion because it wouldn't just be useful for myself, but also for the OP and others.
Whoa! This is a job for the "I Need a New PC!" thread! Definitely not trying to admonish you, you're just more likely to get help there.
All of your concerns are valid, but none of them are issues you'll face.
The Nvidia 1060 has a smaller bus, but fast memory and great color compression. So it evens out. 6GB is more than either card has the throughput to fully utilize.
No one can say for sure which card will be better in future DX12 games. The 1060 is a little faster for DX11 stuff. DX12 won't be fully adopted for a while.
Both the 1060 and 480 will perform worse (in newer games) as new GPUs come out. It's possible that Nvidia performance will drop faster than AMD, but that's in the future.
If you have the money, just pick up what you need now. The 470 might yield more more performance-per-dollar, and it might not. It probably won't come within 10% of 480 speed.
PCIe 2.0 might as well be 3.0 for gaming graphics cards. There will be no real difference. And the 2500K is fine.
FreeSync vs. GSync comes down to one major point: FreeSync monitors are much cheaper. I doubt there will be freeSync compatible TVs, but it's possible. And, to be honest, I don't think either really matters if you're using a wireless mouse and keyboard.
Backplates only matter on long, custom-cooled boards with heavy metal sinks. They prevent the PCB from warping due to heat and weight. Neither the 480 or 1060 PCB extends far beyond the PCIe slot, so don't pay extra for a backplate.
The standard 6-pin PCI power input is still in use.
So: get either the 480 or 1060. The only thing that really matters is cost.