Flexible Demon Witch

Ok, so, character concept is a Witch under the Demon Mythic Path capable of a variety of tactics- in this case, spellcasting with the ability to buff and go into combat with some viability, in addition to cranked up intelligence for hexes and offensive spells.

Character is base tiefling, with Dex 18 and Int 19 as the core stat requirements.

Strength patron, for Divine Power/favor as the luck bonuses from these spells essentially stack with everything (including Transformation) and work with Dexterity based attacks.

Guard background gets me Perception as a class skill and light armor prof.

Core Feats are Weapon Finesse, Piranha Strike, Spell Penetration/Greater, Spell Focus/Greater - 6 out of 10?

What feats am I missing that could help? Is arcane armor training worth it to avoid the spell failure chance if I choose to use mythral chain shirts?

Mythic Abilities planned include Ascendant Element Lightning (for chain Lightning and stormbolts), brutality incarnate (using claws and gore)

Do I go abundant spells x3? Archmage armor, as opposed to light armor? Is brutality incarnate actually useful, with a +3 amulet of mighty fists being available at the top of act 3 and access to the symbol of the inheritor to make my weapons count as good?

Mythic feats planned are weapon finesse, sorcerous reflex, and then maybe spell focus or expanded arsenal (to double my spell focus). Not sure if mythic spell pen is needed, as there seem to be a lot of spell pen boosters available in game…

Hexes planned are Slumber (even if they nerf it it will still be good), iceplant, whatever because I don’t know if I’ll have actions generally for non save or lose hexes.

Game plan is either to sling spells/hexes, of prebuff with divine power/transformation and wade in.

Is it better to stay full natural weapons, or go something like dagger + claw + gore for iteratives under transformation (which loses a lot of stat and piranha strike damage)?

Backing all of this up will be demon aspects focused first on DCs because save or die spells are hillarious.

I am aware nothing here is really optimal - I’m just looking to optimize the concept.