It is a difficult question to answer. For example, I do have some idea about how photoshop works (I have watched a number of talks by one of its principal programmers where he discusses memory management), and it seem that it will use as much RAM as it can for undo/redo functionality. So I can clearly imagine it being able to "fill out" 64GB RAM. But do you actually need 64GB RAM for Photoshop and will it give you any benefits? I doubt it, but it is impossible to know without running a benchmark based on your use case.
There are two basic ways how RAM is used. The first one is what I'd call "working memory" — this is fitting all the data the CPU is working on
right now. Imagine it as having things you need on your work desk. If you have a very small desk, you'd constantly need to run between your workspace and the warehouse, and your productivity will take a big dive. This is the most important reason to have more RAM and that is where people say that it affects your performance.
The second one is using RAM as a cache. Say you have a humongous work desk, so you can put all the items there you need for multiple workflows. This way you can quickly switch from one workflow to another, without having to go to the warehouse. But the important thing here is that you are only working with a small portion of the items at a given time. If fact, you couldn't do all these workflows simultaneously because you are simply lacking the hands to do them
It is similar for CPUs. The CPU in the MBP has two memory controllers, with summary total bandwidth of approx 30Gb/s. What this means that it cannot use the entirety of the memory as working memory (it is just not fast enough) — and has to use portions of RAM at a time. But then again you can use all the excess RAM to "preload" things — after all accessing RAM is still much quicker than loading data from disk. You are not necessarily gaining performance, but you might be improving your latency (time that you need to wait for things to happen). The question is now: will you notice this n practice or is the latency already hidden by something else? One often quoted example where I don't think that more RAM will do much good is browsing. People often say "oh, I have 50 tabs open, I need more RAM". But the funny thing is that the visual animation of switching a browser tab takes much longer than it takes to load that same tab from the SSD cache. So if you "workflow" is switching browser tabs 10 times per second, you might get a noticeable difference with more RAM. In a more normal situation — probably not. As always, you need to try it out.
As for your usage (Photoshop, After Effects etc.), I personally think that the sweet spot might be at 32GB RAM + 2.3 8-core CPU. I doubt that you will benefit much from 8GB GPU, but then again I am not a graphics professional and I don't really know how well these tools can use the GPU RAM.
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