There isn't really a 'bottleneck' with the CPU and GPU but, (finds better words as I was told of for using that word.) There comes a point where you can add a super powerful card with your CPU, and it will perform the same as say the X800gto. But to stop this from happening you can run it on higher settings and resolution.
(Good example, I was playing GT Legends the other day and I had it on medium settings and I was getting around 50fps, I then realised and put it on the highest settings and the FPS were around 48ish. I then overclocked by ~20% and I am now getting ~60
You select on the IDE hdd what you want it to be, master or slave. You don't really have master and slave on SATA, as you only have one cable per drive. The board may have master and slave written next to the sata ports.