Caster Level when Multiclassing to archetypes in the same class

[Sacob]

At level 1, let's say I take the Arcanist archetype Unlettered Arcanist (gives me a familiar, gets rid of the spellbook, uses witch spells). At level 2, if I want to take the School Savant archetype, what would my Arcanist casting level be?

This is assuming, of course, that the two classes wouldn't be mutually exclusive. Please let me know if that is the case (I don't see why it wouldn't be, they don't alter the same feature at all) so I don't go too far down this rabbit hole :P

[kestral287]

You can't take multiple archetypes with conflicting abilities, so this can never occur. And you can never multiclass into the same class. Once you've selected your archetype or archetypes for that class, they're fixed (barring retraining).

Archetypes can be stacked only if they replace entirely different class features with zero overlap. In this case, you'd actually be a School Savant/Unlettered Arcanist 2, since none of their alterations overlap.

But you could never add in, say, Blade Adept, because that has overlap with School Savant.

[Chess Pwn]

Also you can't take levels in a different archetype. You can't go blood arcanist 1 and then next level take school arcanist 1. You can only increase your arcanist level, not start over on a new entry of arcanist.

[Lakesidefantasy]

It appears that the two archetypes are compatible and are not mutually exclusive. Although they would both need to be taken at first level.

It also appears that your arcanist level would be treated as both your wizard and your witch levels to determine school and familiar abilities granted by those archetypes. So, at second level your casting level would be 2nd.

You would be an arcanist (school savant/unlettered arcanist) 2.