mParticles Flow creates a simple Particle Flow setup that is wired for MassFX simulation; just play the animation to see the physics simulation.
The flow comprises two events: one global and one local, similar to the Standard Flow setup.
The global PF Source event has the Quantity Multiplier settings for both Viewport and Render set to 100% and Integration Step for both Viewport and Render set to Half Frame. This is done to have the same amount of particles in render and viewport; and have the same integration step, thus ensuring that the rendered simulation works the same as the viewport simulation.
The local event, Event 001, contains the following operators: Birth Grid, Shape, mParticles Shape, Spin, mParticles World, and Display.
The Birth Grid icon is positioned 60 units above the ground, and its size combined with the Grid Size setting are calculated to generate 100 particles.
The Shape operator is set to the Cube type, with its Size value slightly smaller than the Grid Size setting in the Birth Grid operator. This prevents particles from colliding at the moment the simulation starts.
The particles are set in mParticles Shape to collide as boxes.
The Spin operator has a low Spin Rate value to create a random small spin for all particles. This enhances the simulation effect, because particles move slightly differently from one another and do not copy or clone each other in their relative motion.
In addition to the mParticles World operator, the preset creates a mParticles World helper (the simulation driver) and associates the two. The mParticles World helper has both gravity and the floor (Ground Collision Plane) enabled, and is positioned at Z=0.0.
The Display operator is set to Geometry, because with simulations it's important to see the actual particle shapes in the viewport.
Last but not least, Real Time is turned off in the 3ds Max Time Configuration settings. So, again, you can just play the animation and see the simulation with optimal settings immediately.