Help Me Understand NPCs on the Back End

Greetings, all! I ask you about these now because I want to help make the recruitable NPCs in this game worth using, but that means understanding them enough to change them.

1: For NPCs, what IDs/spell codes are used when determining what spells a creature knows? For example, if a Wizard knows fireball and knock, what spell IDs are used?

2: For NPCs with class levels, does giving a unit a class level also automatically give it the relevant class features? If not, what class features are auto-granted?

Thankee!