Total novice, first post...

New Mitsubishi 18K mini-split heat pump installation with ducted horizontal indoor unit (variable speed fan).
Single return, multiple supply runs in star configuration (for better air mixing).

For best efficiency and lowest noise, should the cross sectional area of each supply duct be the same as the free air space of the register it is driving or can it be bigger (to reduce friction through the length of the duct)?

Is there an optimal face velocity for a floor mounted (heating) register assuming an eight foot ceiling?