Increasing maximum available memory testing. How to get better results?

This is a i7-8700, 32Gb of RAM, NVIDIA GeForce GTX 1080, running Windows 10 and Java 8 (171) installed and heap memory set to max 32Gb(-Xmx32g) (?) on run parameters.

I think this is not a question about library. However, as experiment, I am running an example from box2D library for processing named Liquidy.pde where I changed the sketch sizeto (600,300) and tested 3 renderers (default, JAVA2D and P3D). P2D was way too slow to be considered at this point.
I am printing the total memory, allocated memory, free memory, n of particles, fps in the title of the sketch.
I am also declaring the sketch to run at 60 fps using frameRate(60);
I have tried to increase maximum available memory, but when the option was disabled, I have got a slightly better performance in fps.

When running the sketch, a click of mouse will generate a particle system.
10 clicks would generate an environment with about 1000 particles, and 15 clicks will stay around 1700. See attached picture:

With 10 particle systems, each rendered kept sketch running around 60 fps:JAVA2D a little worse than default. P3D performed just a little better.
for 15 particle systems, frame rate will decrease to 15 fps (P3D), 19fps (JAVA2D and default).

Disabling the “increase maximum available memory” in preferences (and restarting?) made default renderer and JAVA2D to perform a little better when running 15 particle systems. From ~20fps, they jumped to 25fps.

I am not running out of memory and I wonder if there is any way to improve the performance of my sketches.