http://www.pcgamer.com/gta-5-system-requirements-announced/
What the "bottleneck" is isn't completely certain. It appears like the game will run reasonably well if you take your time to tweak the settings for the best experience.
Also, where the bottleneck is in a system not only varies between games a lot but can even switch during the same game. For GTA5 it looks to me like the GPU and CPU are roughly balanced so it's possible the bottleneck might be the CPU at times and GPU at other times but that's a guess.
You can also try googling Youtube for similar systems running GTA5 and see how they do. Your CPU portion of the APU is probably similar to an FX-4100.