You would be ill-advised to try and OC that gpu, as they are already pretty much already set to the maximum they can take in regards to heat etc., and are known to already run very hot at factory settings.
The build quality is pretty good.
If you game at a lower resolution but within the same aspect ratio (16:9) it won't look stretched but you will have some blur.
In my opinion 17" add's a ton of weight compared to the little bit of screen real estate you gain. Since it isn't really portable you are much better suited with a desktop and a cheap laptop for on the go. If a laptop is the only option you are considering then personally I would save up a little more and get a Y580 with the 660M and then pair it with an external monitor and keyboard when you aren't using it on the go.