1) No not yet, the only currently available PSUs with the native connector are the Gigabyte GP-UD1000GM and the MSI A850G, A1000G and Ai13000G models. It's also worth mentioning that Corsair sells and additional 12VHPWR cable for their PSUs though it's not "native" and they are still ATX 2.3 designs. (for MSI PSUs just make sure it says ATX 3.0 and it'll have the new connector) Like the one I have here:
 https://www.newegg.com/msi-mpg-a1000g-pcie-5/p/N82E16817701016?Item=N82E16817701016
 
2) mostly irrelevant, they are very close the performance will be nearly identical, get which ever is cheaper
 
3) that depends on your budget but good brands are ASUS, MSI and Gigabyte they all have boards in the $300 range that are well built with solid VRMs and feature sets.
 
4) nearly no difference between i5 and i7 in games and no a "KF" CPU has no integrated graphics so it cannot output a display without it, you will need a discreet GPU of some kind installed to output video
 
5) for gaming this is also irrelevant, just grab a 980 Pro as they are still more than you'll need for gaming, have a built in DRAM cache and conveniently just went on sale for $109 - $119 for 1TB models
 
6) all of the RTX 4090s are pretty cool and quiet despite their gargantuan size. Just get one at MSRP and you'll be good to go. They all stay in the high 60s low 70s at full load and can all seemingly reach about 3Ghz core clock on the stock air cooler
 
7) yes, just install Windows 11 by downloading the Media Creation Tool here:https://www.microsoft.com/software-download/windows11 Just direct it to a USB drive and it'll make you a bootable ROM, when it asks you for your product key just enter your Windows 10 key and it'll activate just fine