If you just play fortnite that game is very badly optimized for high core / thread count. In comp fortnite scene most people actually disable hyperthreading even with intel processors to gain higher overclocks .
Even older 900 series can run this game on 300+ fps stable with 1080p competitive settings, this depends on cpu single core performance and ram speed / timings.
With 2060 / super you can max out 1440p at 240 or 360 framelimit (this video he turned off hyperthreading so running only 8 cores) running with RAM: 3733MHZ 14-15-15-28 :
View: https://www.youtube.com/watch?v=8E9QMEL5Yo0
Like logainofhades said 10600k would be better choice for the future, i would never pick amd if i ever touch competitive fortnite. The core count is really fitting 6 cores 12 threads and you have upgrade path.
For gpu, pick atleast 1660 ti thats enough for 1080p , maybe 2060 / super for 1440p depending on what graphic settings on you like to play, and if you play other games too. This is with 240-360hz monitor, if you go lower than that like 120-144hz monitor / 1080p or 1440p then even gtx 1060 & 1650 super is fine.
If you want to reach 240fps+ stable endgame / midgame you need this paired with fast ram + good timings, motherboard should support overclocking and higher ram speeds. If your only gaming 2 x 8gb with xmp is good. Just look ram compatibility from motherboards manufactor site, 3600mhz ram with lowest timings running in dual channel go for that.
With higher ram speed / better timings and faster cpu clock speed it just keeps scaling up (hyperthreading disabled 10900k + 4600mhz ram) :
View: https://www.youtube.com/watch?v=N0YwSu8AYww