Slitherine

I'm working on two Bronze Age armies & I'm not sure about subsidiary weapons for chariots.

Specifically, NKE chariots are, of course, bow armed. Do they get light spear for melee?
Equally, Later Mycenaean chariots are light spear armed. Can they throw javelins as well?

No to both, bow armed light chariots and spear armed light are an evens fight in melee and light spear is for impact, not shooting.
The light spear would count in impact, neither have a POA in of themselves, so the "mounted light spear +" counts giving the Mycenaeans the advantage in that phase only.