So I know that if one gets spell point powers from multiple sources (e.g. multiclassing cleric and taking domain) your total amount of spell points are calculated based on whichever is attribute has a larger bonus.
But do I maintain two separate Key Spellcasting attributes? Do I use whichever is higher? Or do I use only the one from the first class?
You do have two key spellcasting attributes, one for the primary class and one for anything gained from the multiclass.
This question only comes up if you take multiclassing feats. In that case, the relevant feats have this language in them:
"If you already have a pool of Spell Points, use the higher ability score to determine the pool, as normal, and your Spell Point pool increases by 1."
This question only comes up if you take multiclassing feats. In that case, the relevant feats have this language in them:
"If you already have a pool of Spell Points, use the higher ability score to determine the pool, as normal, and your Spell Point pool increases by 1."
But the question is "If powers from class A refer to a key spellcasting attribute, and powers from class B (achieved through multiclass feats) refer to a key spellcasting attribute, are those the same attribute, or do I have to track which powers are from which sources?"
For example, if I'm a Paladin who multiclasses wizard and gains the evocation arcane school through the "Arcane School Feat" then Lay on Hands says "you restore Hit Points equal to 1d4 plus your spellcasting ability modifier" and Force Bolt says "Make a ranged touch attack against the target to deal force damage equal to 1d4 plus your spellcasting ability modifier." Are these the the same ability modifier? Is one Cha and the other Int?
One is Cha and the other Int. You also have separate spell proficiencies if you're a double caster - a Wizard (Cleric) of 16th level has expert proficiency with Arcane spells but only trained with Divine.
The other annoying thing is that while cantrips scale with your level, any domain/school powers do not, they're still limited in autoheightening to your max (archetype) spell level. Between that, secondary casting stat, and no proficiency growth they aren't a strong option in many cases.
I feel like having two different modifiers for spell slots makes a lot of sense, since you track your wizard spell slots differently from your cleric spell slots (you can cast fireball with one but not the other). But for powers, since they use the same resource pool, which is fed by only one attribute, it feels wrong to have to track two different attributes.
Like as it stands a multiclassed Paladin/Cleric could have no spells beyond cantrips, but domain powers chosen from the same set of options which refer to different ability modifiers. Like "My Fabricate keys off of Charisma, but my Divine Ward keys off Wisdom, or was that the other way around?" for a Shelynite Pally/Cleric.