in case you haven't already bought it, I would go with an unlocked i5 so that you can overclock down the road if you need a faster processor without buying a whole other cpu.
to the topic at hand, I would go with a 1070, it seems it would fit well with an i5. if you want the 1080 would also be good, the CPU might bottleneck it in some areas but not so badly. since youre getting 144hz, you would very much benefit from higher framerate. you can watch Linus' latest video on bottlenecking and make a decision as well.
You can also wait until NVIDIAs new card lineup, Volta as Pascal is already a couple years old.