Tips for performance from n00854180t :
Make sure to turn off dynamic shadows for most things
* Turn off collisions between static actors
* Turn off gravity for static actors.
* Make any non-moving level geometry *static* (not movable).
* Reduce the number of lights that cast shadows.
* Keep GPU particles to a minimum, or use lowest LODs for GPU particles, and no scene collision.
* Use no more than one particle light node.