'bottleneck' simply means one component of the system can't keep up with the rest of it.
A low end CPU with a high end GPU....the CPU can't keep up with what the GPU wants to do.
or...1GB RAM with a killer GPU and CPU....the RAM is the 'bottleneck'
How to tell? Monitor usage. Under load, if the CPU is maxed out at 100% and the GPU is idling along at 30%, the CPU may be the limiting factor in the system.
You want balance.
Your CPU and GPU are fine.