So, I've been having problems with AE and NVIDIA since I upgraded to CC 12.1. First, the app wouldn't recognize the Graphics card (Quadro 4000 for Mac). I then updated the driver for the card, upon the suggestion of other users. Now, when I launch the app I get a warning: "the GPU Accelerated ray-traced 3D renderer does not have enough free video memory", which doesn't make sense for I have 24GB of RAM, 10.8.5 and a 6-Core Mac Pro! Sooooo irritating!! Someone from Adobe suggested to other users with the same problem to quit the web browsers while working with AE. C'mon, that's ridiculous! So I have 24GB of RAM on my machine and I can't have two apps running simultaenously???
RAM and VRAM are entirely different. The latter is the amount of memory on your video card. Your video card has barely enough memory to use the GPU acceleration features under even the best of circumstances (1GB). The recommendation to not run other applications is because other applications are consuming part of that very small amount of VRAM.
The After Effects CC (12.2) update and After Effects CS6 (11.0.4) update include fixes and changes regarding the OptiX library for the ray-traced 3D renderer that make VRAM handling better, prevent crashes, and otherwise improve the experience in this area.
Let us know how it's working for you after you've installed the updates.