So yeah... just running 2x20 is much more efficient. MRM10s seem to be kinda disappointingly hot. Can also make it asymmetric for getting more tonnage (for example extra ammo or higher engine)
Does the MRM10 x4 fire faster than the MRM20 x2? It seems to me sending all those missles out in a quick vollet has a lot of utility.
Nope, same cooldown and the firing time has negligible difference in duration. 4xmrm10 is just 33% hotter and 2 tons lighter than 2x20 (which you spend mounting extra heat sinks) and you can chain fire it better if desired.