As I said before and you didn't even close previous forum threads, the i5 is almost the same especially overclocked, the i7 only gives you better performance in other stuff like installing games, streaming, archiving files, doing workloads or stuff, etc.
For gaming only if you don't have the money, get a i5. Otherwise get a i7, you get more cores which may benefit any unforseen future needs. 8th or 9th generation is all the same, just pick one you like, the 8th is cheaper and is a bit more reliable since it's been out a while.
If you have money just laying around, get the 9700k.
For Fortnite only as I already told you and showed you a video, the Ryzen is just under Epic 144 fps. So the 8600k is good enough, the 9600k (same with the...