it'll be so bad, the GPU probably hover around 20-40% GPU usage while the CPU maxed out (occasional 50% usage perhaps?)
here lemme tell u my experience in GTA V with a G850 bottlenecking a 1050ti:
i can easily reach 60 FPS with that GPU, BUT, with the bottleneck, my FPS hover around 20-60 so much that it stutters everytime i look around, so guess what, i had to cap it to 30 fps, in order to play it, and it'll still dips to 20 from time to time, even came way down to 14 fps at certain part....
the 1050ti usage hovers around 30-50% with some occasional 60% peak for a few second
while the pentium stays 97-100% most of the time
now if u really prioritize the streaming power, better upgrade the CPU first, as the RX 460 should be able to hold up as long u're willing to tune down some setting in order to prepare some headroom for the streaming part:
i personally rather stick with the R7 1700 (the non-X): it consumes less power than the X one, had stock cooler which u can use till u can afford a better CPU cooler, and u can just tweak it to reach the X version's performance
OR
Coffelake's about to come, so u can just wait for that if u're considering an intel alternative too