I mainly play Gta Fortnite and Rocket League is the i5 sufficient or should I prefer the I7 because of 8 cores and more threads.
The Intel i5 10600k is easily sufficient for your purposes.
Stream on the side?
Then the Ryzen 7 3700x would be interesting from a price-performance perspective
The i5 is completely sufficient for gaming alone, and actually doesn't need a "k" CPU (i.e. One with K at the end of the name).
If you want to do a lot on the side (video rendering / streaming), you should use Ryzen. (Especially with the newly announced CPUs coming in November.)
A Ryzen 3700x should be enough.
Yes, but if you didn't go for price performance now, Intel would be better right?
The Intel has more power, but this is not absolutely necessary for your purposes
