This is what I found works best with me. I used the actual lineart part for the color drops. On your map, it would probably work best if you did the non-land parts in a white, then the larger land masses, then creat another layer under the lineart and did a full color to get all the small islands.

Yes, can I send you a PM video of how to do it? It’s hard to explain

That study is misrepresented: the brain continues to change throughout life, the people conducting the study just cut off tracking at 25.