Hello,
I was wondering if that's a bottleneck or if there's a problem, but I bought 2 weeks ago an RX 580 of 4 GB. Before this one, I had a GTX 960 of 4 GB, and this graphic card run csgo at 200 fps, meanwhile, actually, the RX 580 is giving me in some maps of csgo 150 fps, but in the most basic one, the one that gave me more fps with the GTX, is giving me between 40 and 70 fps. I have an FX-8350 with a ga-970-gaming motherboard, cause that I wanted to ask if it's due to a bottleneck.