Hi there!
· Something is wrong with RNG in render mode. It looks good in preview but when it renders the animation most of the particles are going in the same few directions.
It's a necessary evil so it can be seamlessly looped, it's more noticeable on shorter renderings. It should get improved at some point.
· it feels like the burst doesn't work correctly - it should spawn all particles in the same time. Instead it spawns them one by one. Maybe I'm missing a feature.
There's an option in the "Basic" tab called "Particle Number", I think that's what you are looking for.
· Setting up sprites as particles breaks the animation - basic options like rotation, scale, life don't apply anymore.
Built-in particles and sprite particle don't share some configurations, this is something that is on the roadmap and one of the first things to be reworked after bugfixing.