It was my mistake, I'm sorry. I have made some tests in BG1 now and you have right: for ADD_GAME_NPC the NPCLEVEL.2DA also get applied.
I have another question. What means "parchment" in LeaveAreaLUA (S:Area*,S:Parchment*,P:Point*,I:Face*)? In mods suitable for both pure BG1 and BGT/TUTU parchment is used for BG1 Version but not in BGT/TUTU. Maybe it schould be added to this tutorial, but what is importance of that?