floyd rose and studs

Hi
i have talked with many people about it
but some told me that the floyd rose must be 90° (perpendicular) to the studs and somebodys told me the floyd rose bridge must be parallel to the guitar body

now i have seeing in several guitar like ibanes studs not fitted perpendicular to the body

a lutist told me the Saddle must be parallel to the body , in this case the bridge is a little down
so may i know please the true?
i have just started a new guitar re-born :roll:
thanks