Gaming summary- If planning on a very good GPU and possibly using a 144 Hz monitor, the 9700K is usually capable of better framerates. ('very good GPU' defined as, for instance, a, GTX1080/RTX2070 and above). With mid-range GPUs ( GTX1060/RX580-class), the frame rates would not matter as much, especially if using a 60 Hz monitor...
Additionally, if 4k gaming on newer games, the GPU becomes ~98% the determining factor (avoiding the term 'bottleneck'!), and, framerates would again be nearly identical for most CPUs of R5-1600/i5-8400 and up...