Moving my recent thread derailment to its own home here.
General question - when your form changes to another form due to a polymorph spell, how does your new form vs your natural form influence what spells effect you?
Specific example: I am a humanoid. I use Plant Shape to become a plant creature. I am hit with a Horrid Wilting spell. Do I take 1d6 per caster level or 1d8 per caster level?
Your type does not change unless the spell explicitly says so. So a humanoid that uses plant shape is still a humanoid for all purposes.
If you are an elf and have a polymorph spell cast on you, you still count as an elf. So, you would be affected by all spells as though you were an elf. Or whatever you were originally. Polymoprh does nothing to change that.
One exception I can think of is monstrous physique. If you use it to turn into an aquatic creature, you gain both the aquatic and amphibious subtypes. But this is a good example to show that your type is unaffected unless the spell says it is.