[quote=Asuras]
So how is it decided how much EXP is gained for including a flaw during character creation? Also how it will influence rolls.
[/quote]

It's usually just a guess between +1 to +3 XP per flaw (though you can only have a maximum of +6 from all Flaws total, even if you have more Flaws than +6) based on severity. If it's too high or low, the GM will suggest changes.