How does the Quick Study exploit work for a School Savant Arcanist?

Question

I have an arcanist character with the School Savant archetype, which allows me to prepare an extra spell per level of the chosen school (Air in my case) but requires two preparation slots for a spell of the opposing school (Earth for me).

I also have the Quick Study Arcanist Exploit which lets me swap a prepared spell for a different spell in my spellbook.

The interaction of quick study with these school spells are not exactly clear. For example:

• If I choose to replace a specific Air school spell that I prepared, am I restricted to choose another Air school spell as a replacement?
• Can I replace a normal spell with an Earth school spell, thus bypassing the need for 2 "preparation slots" (or do I need to replace 2 spells perhaps, or something else)

So how does replacing prepared spells with Quick Study work when both specific school spells from School Savant and other spells are involved?

Answer 1

Those extra spell slots are restricted to [Air] spells

The School Savant extra slots work similarly to domain slots, you may only prepare that specific type of spells in those slots ([air] descriptor spells). When you use the Quick Study exploit, you are able to prepare another spell on that slot, but any existing restriction on that spell slot is not removed, including the spell level and the type of spells that are possible to prepare on that slot.

If you are replacing an [earth] spell by another, you will free two slots. And if the new spell is also an [earth] spell, it will consume both of those slots. If not an [earth] spell, then it will consume a single slot and you will have one free slot, which you may prepare any spell you want by taking some time reading your spellbook later.

Otherwise, your other slots (from the arcanist class) are not restricted and you may freely choose to prepare [air] spells on these general slots using a single slot per spell, and you may also freely replace them using Quick Study. The [air] descriptor restriction only applies to the extra slots granted by the archetype. If you don't have two free slots, you cannot prepare [earth] spells using Quick Study, as those spells require two spell slots to be prepared.