Im dont know which one to go for . Would 2600x handle streaming 90% of games on maximal graphics with gtx 1080 on 60fps+ or should I go for 3600?
Yes, the 2600x would be enough with a GTX1080 for pretty decent in game settings and good quality stream output, with very little by way of dropped frames. The 3600 is a bit better IPC and so is about 10-15% percent faster, depending on the game/application being used.
Most gaming/streaming systems would use a 3700x with 8c/16t , or Intel I9 9900k/s for absolute best results. But 6c/12t is enough for now at 1080p.