Dragon Age: Inquisition on an External Hard Drive & Macbook Pro

Hi! I'm not very good with computer things, but I love games.

I got a Macbook Pro (retina) 15" for my birthday in 2012, and since then I have set out to turn it into a gaming laptop, with mixed results. I can play Skyrim on Ultra graphics, but I had to download a wineskin to do so. ((EDIT: I was using CrossOver and bought a lisence to it in August of 2013, and since then they have updated so often that my lisence is "outdated" and they won't allow me to use it at all, so I have to keep downloading the trial version... pretty irritating. Hence my need to just buy Windows, which I probably should have done in the first place. Ideally, I wouldn't have gotten a Mac at all, but my dad got it for me on the advice of my high school art teacher, and I'm not even majoring in Art...nor do I have a tablet. Seems pretty pointless to me, but oh well. I don't have the money for a new laptop, my status is "broke college student," so please bear with me.))

Anyway, I was going to buy Windows 8 and then run Bootcamp, sectioning off ~100gb for Windows, and then was planning on installing games onto an external hard drive.

However, I'm not sure that this would allow the games to run as smoothly?

My setup is as follows... (I'm just copying what shows up when I click on "about this mac")

Processor: 2.6 GHz Intel Core i7

Memory: 16BG 1600 MHz DDR3 (I have 500gb internal memory/SSD)

Graphics: Intel HD Graphics 4000 1024 MB && NVIDIA GeForce GT 650M 2014 MB

and the OS would be Windows 8.

The external hard drive, which I haven't bought yet, would be at least 1TB and either USB 3.0 or Thunderbolt.

Can anyone break this down for me, or does anyone have experience with this setup and Dragon Age?