some basic questions about BCs and pressure

Dear sir or madam,

I am making models about laminar flow and thin-film flow. I saw the velocity boundary condition
in thin-film flow is called "normal inflow velocity". What is the difference between "normal inflow velocity"
in thin-film flow physics and the "velocity" in laminar flow physics?

By the way, in model inputs, I saw two options to set the absolute pressure: user defined PA and PA=P+Pref.
Can I get the same results if I set PA =1[atm] in the first option and Pref=1[atm] in the second one?

Thank you very much.
Best wishes