Particles VFX video with transparency

Starting from my knowledge of standard VFX tools such as AE want to try using Unreal to create some small video involving particles. Unreal particles appear to be really efficient in using resources and powerful as features, so cutting the hours needed to setup and render Nx10k particles in traditional tools.

I want to do these things: setup a particle system hitting a simple cube, with friction and secondary emission, render the animation to a video with transparent background so to be able to composite it further.

I can’t find a way to control the particle system main parameters from the sequencer, nor to generate a video with alpha channel.

Can’t understand if these are standard features, or need I to know some trick.