Don't think that you need to see all of your RAM used all of the time. If the CPUs are at 100% and the RAM usage is at 15%, then this just happens to be a rendering task that is not RAM-intensive.
Follow the link that I provided earlier, and read/watch the resources that it points to. For example, this video introduces the idea of bottlenecks in processing, which is relevant to what I just said above:
http://www.video2brain.com/en/lessons/overview-of-data-flow-and-common-bott...
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Todd Kopriva, Adobe Systems Incorporated
After Effects quality engineering
After Effects team blog
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