Hello world, first post here.
I am in the process of transitioning from PS to AP and opacity dynamics are integral to my painting process. Honestly I wasn't satisfied with the offered solutions, as the proposed brush settings yielded nothing like PS behaviour, but I managed to find a solution.
All the buildup and flow tweaking still resulted in a situation like on the left half of attached image ("Like FLOW dynamics in Photoshop") - something like a semi-transparent tube sock where each brush stamp is drawn additively over the previous one, resulting in a very quick buildup. Notice the stroke overlap in the squiggly line and poor tonal range in the other one as I brush from very low to full pressure.
The solution was to set Luminosity Jitter to Pressure. Even a very low value will do and you can play with the curve profile. The result is very similar to Opacity dyamics in Photoshop - no more sock tube and you get great tonal control. Now if you pick a colour and brush at half pressure over another, you easily get a mid-colour between the two, which I find is a very common situation in digital painting.
Hope this is helpful to others, and do let me know if there is a simpler/better solution!