http://wccftech.com/kaby-lake-pentium-radeon-rx-series-gaming/
According to this, the G4560 bottlenecks the RX 480 in Watchdogs 2 and Ashes of the Singularity. However, in other games like Doom, Titanfall 2 and RE7, there is very little (sometimes next to none) bottleneck.
The decision is yours. If you are comfortable with the price premium for a more powerful GPU while accepting that there will occasionally be a bottleneck, you should go for it. Otherwise, an RX 470 should be sufficient and, in this scenario, should give you more bang for your buck.