It would work. Note that the i7 6700K does NOT come with a cooler! So you have to buy a CPU cooler to run the PC. I would recommend a fan cooler from Noctua, or since your case has a side window, one from "Be Quiet". All-in-one water coolers are top in terms of cooling performance and look good, but are louder (and somewhat more expensive) than high-end CPU air coolers.

As Eddimor already said, installing a 1000W power supply is a bit heavy for a single GTX 1080, but everyone has to decide for themselves. Have fun with the system ;)

I think so. The power supply unit may even be a bit strong, but it certainly won't do any harm. But I would get a more casual cooling system for the processor. But logically, it's not mandatory.