... You're talking about the "new" Mac Pro from 2013, right? Pretty much anything can play CS:GO. An Air is probably the only thing that would struggle with it. Older Minis too maybe. But a desktop computer like the Mac Pro? Of course it can. Depending on the GPU you choose for it, you can also play very high end games (albeit with Windows for dual GPU support in games). With dual D700s Battlefield 4 can almost run fluidly in 4k Ultra, and if you go down from Ultra it'll run perfectly fine in 4k. High will probably do it. The difference between a Fire Pro and a Radeon in gaming performance, running the drivers meant for each card, is probably around 15% for the same GPU.
Yeah, it can too. As I said in my post, only the Air and perhaps older Minis wouldn't be able to. When you say base, I assume you mean 13", which means the lowest end GPU possible. Will still run it though I don't know if you can go max-settings