What determines the kind of soul that an actor has? I've looked all over the Race form and haven't seen anything to that effect. Am I just missing it?

Great Question!

Sadly, no great answer

Do you know, you may be the first person to ask this ... and after 8 months of the CK that takes some doing

I don't remember ever seeing a setting on Race, Class or Actor ... So I suspect it is hard-coded, somewhere ... Maybe via Level, or size, or Boss-flag/Keyword ... I'll have a look in the CK when mine's open later

(if no one else knows ... ?)



The sizes are here: http://www.creationkit.com/Soul_Gem ... But the wiki is silent on who gets what size and how ... (sort of matches with Justin''s line-up ... sort of ...)

Given Justin's post, it appears the level of an NPC effects the size of the soul??

I believe they're handled with Game Settings:

• iPettySoulActorLevel: < 4 <-This one doesn't exist
  
• iLesserSoulActorLevel: 4
  
• iCommonSoulActorLevel: 16
  
• iGreaterSoulActorLevel: 28
  
• iGrandSoulActorLevel: 38

I assume what Justin says is correct for animals, that's what I used in my mod too.
Would add that humanoid (black soul) have no such level distinctions at last from soul trap pov, they always have the same charging value regardless the level or anything else.