Display Acceleration Disabled

The solution you're referring to is a years old workaround for a feature that's no longer in After Effects (the Ray-traced 3D renderer). It has nothing to do with the warning you're getting about Display Acceleration being disabled, and this is also a separate warning from the Mercury GPU option in the Project settings.

For starters, check to see that the "Hardware Accelerate Composition, Layer and Footage panels" preference is enabled. This option is controlled in the After Effects preferences under the Display tab (it's the third checkbox). 

Otherwise, the best option is likely to update your GPU driver. Again, this has nothing to do with Nvidia or that workaround you found, just go to AMD's site and install the latest driver for your GPU.

This is a warning saying that After Effects is unable to use your graphics card.  I've noticed a lot more success with Nvidia than AMD unfortunately.  Are all GPU drivers up to date?

You don't have to use graphics acceleration, you can disable this by going to Edit > Project Settings > Video Rendering and Effects, then select Mercury Software Only.

Software which uses the computer's GPU can sometimes run into problems like this.  I always explain it (and this might be completely wrong) but a graphics card is designed to run 3D games fullscreen and optimised to reduce live issues such as lag etc...  But After Effects is a frame by frame process and will "happily" spend a minute on a single frame to get it rendered.  I think this can cause a conflict between a GPU and AE.