Nitrous Fittings 6an Or 4an Please Explain.

Typically, the 4AN is dedicated to the higher pressure N2o stuff, and the AN 6 stuff is for the lower pressure, higher volume fuel stuff.

But,

if it was a big power system system all of the typical goes out the window.

A street, or mid power system will be as I described. rarely do you see -6 going to nitrous solenoids excepting the bottle feed to a distribution block. I cant imagine why they'd give you an option.