To be a little more specific, as far as I know they were light cavalry. Does that mean their primary battle focus would have been ranged fight?
What was their equipment (how many throwing spears did one soldier carry into a battle)? Where did they keep those spears when they were fighting?
Would they have been used in the pursuit of disorganized fleeing enemies?
What was their role in combat? Did they attack before meele Battle between Formations started? And what would they do during the battle, I imagine throwing spears into fighting Formations could very well injure your own troops. Also you can carry only so many spears, what would they do once they had no ammunition?
I cannot speak for the equipment or individual fighting style of the cavalry, but I can perhaps shed some light on the final point.
During the second Punic War Hannibal deployed his formidable Numidian cavalry seperately from the rest of his force, most famously at Cannae. Here whilst the Romans engaged the Carthaginian infantry Hannibal sent his cavalry to engage the Roman cavalry, where they forced them from the field, and swept around to encircle the massed Roman infantry. Livy includes a story where the cavalry pretend to elope onto the Roman side, but secretly have daggers hidden under their cloaks and attack the unsuspecting Romans - the story is however most likely false.