There is no "correct" size, only varying sizes for different media that is sprayed.
Most airbrushes work best with a medium needle/nozzle combination for modeling, such as the medium Badger and Paasche needles.
The size of the needle and tip do not dictate how thin of a line the airbrush will spray. That is determined by the taper of the needle and not the diameter of the nozzle.
The HP-CS will work just fine as will the Omni 4000, Badger 100LG and several others in a similar category.
Mike
“Wisdom is the right use of knowledge. To know is not
to be wise. Many men know a great deal, and are all the greater fools
for it. There is no fool so great a fool as a knowing fool. But to know
how to use knowledge is to have wisdom. " Charles Spurgeon