Maybe an MMO like World of Warcraft, but an overclocked 7600k +1070 would still max out settings and hold 60+ fps most of the time. But in a game like that, no CPU could hold 60 fps at all times in a 25 man raid or congested major cities.
The 7600k is nearly as powerful as the 7700k. The overclock might be 200Mhz lower and it has 4 threads instead of 8 on the 7700k. But the exact same IPC.
The 1070 is much more powerful than the 1060. So for GPU intensive games, it will perform much better. At 1080p, your friend is future proofing his rig for a while. Or he can even go 1440p in the future if he wants. Where the 1060 would struggle with that.