You are using an out of date version of CC 2014 and there are a couple of versions of CC 2015 - you'd need to specify which you are using. (You should be on 13.2.x for CC 2014, 13.7.1.x for CC 2015 and 126.96.36.199 for CC 2015.3 - and yes, you can have all three versions installed alongside each other.)
You should not be editing any .txt files. Ticking that box should make that GPU accelerate rendering of the ray-traced renderer in both versions of CC 2015. No matter what you do with that .txt file or the tick box, you won't be able to use that card on CC 2014. (That card uses a newer OPTIX library that wasn't implemented in AE CC 2014.)
That being said, the ray-traced renderer is considered obsolete by the After Effects team. I would recommend against being too reliant on it.
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
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