First build high end dual boot PC (advice requested)

[bobthebuilderx86]

Hey everyone!

I'm planning to finally build myself a good PC (I'm still running a 2007 iMac). I'm reasonably mechanically minded, and like a nice challenge, so it seemed like a good idea to take on the task of building it myself. I started digging around a bit, discovered the hackintosh database and was immediately excited. I do plan on using the PC for some games - I'm not a fanatic gamer but right now I can't play along with most of them - and a bit of foto editing, and as those programs generally run better on Windows I thought dual booting would be best. I made up a list of parts I'd like to use, trying to keep the overall cost as low as possible by using second-hand parts whenever I can. I did aim for a high-end PC that is durable for the upcoming years, and is a significant improvement to the PC I have now and a midrange to high-end laptop I'll have to buy in the future for my study. I'd love to know what you think, whether I missed some potential issues or where there is room for improvement.

This is what I had in mind:
CPU: Intel i7-6700K Boxed (possibly another gen could be better in combination with the other hardware?)
GPU: Sapphire Pulse Radeon RX580 8GD5 6GB
Motherboard: ASRock Z370M-ITX/ac (I found a build where this was combined with the same CPU and GPU, so I figured they would match)

Note: Someone else pointed out that this version of the i7 is not compatible with this motherboard version. Would you recommend changing the motherboard to Z270, changing the CPU to I7 8700k or just using a different type of motherboard altogether?

RAM: 32GB DDR4 - 2x16GB (if everything becomes too expensive I'll scale down to 16GB)
Storage: 1TB SSD (if I can manage the cost, otherwise 500GB) - partitioned for dual boot on a single SSD
2TB HHD WD Elements
Case: Sharkoon RGB Pure Steel - fans included
CPU Cooler: Scythe Fuma 2
Power supply: Be Quiet! Power 9 700W - I think I will need at least 700W for this system, but correct me if I'm wrong. If there are better systems to be found, I'd be interested in that too!
Monitor: Undecided, a big market. Also depends on the final parts I'll use.

I'm most uncertain about the combination of CPU, GPU and Motherboard. The latter I selected based on the combination of CPU and GPU, rather than it's individual strength although it seems sufficient. I'm also not sure about the CPU Cooler and Power supply, hard to say how fancy it needs to be. I would prefer to buy things second hand, but if that's not a possibility I'll buy it somewhere online. I have a mac that runs on El Capitan, so I'll start with installing that OSx but afterwards I intend on upgrading to Catalina. I tried to pick parts that combine well with the MacOS operating system, to get into as little drivers or kext issues as possible. I'm not afraid to get my hands dirty with hacking a bit, I just don't have a lot of experience in the field so I'd have to rely on tutorials online.

Thank you in advance for thinking along with the project!