my i7 7700k runs from 4.2 ghz to 4.7 ghz and i wanted to know if it bottle necks my rtx 2080 and if i should upgrade to a i7 8700k
As long as it is just gaming (with no streaming workloads), the 7700K is still quite adequate/good/relevant, and in fact,, still out frames almost all Ryzens in the vast majority of games....
(The TechPowerup link comparison above used a 1080Ti, a still fine GPU, but, naturally there might be a bigger disparity in CPU scaling with the very best GPU, i.e.., a 2080Ti...)
Here is another cross section of gaming results comapring different CPUs, but, using a 2080Ti...(shows still very good results with stock on OC'd 7700K), but shows up to 35-36% improvement in some games' (FarCry at 1080P) average frame rates comparing stock 7700K to stock 9900K, and the difference shrinks to 29% when both CPUs are overclocked