Is ahrim wand and book much better than polypore staff? Is ahrim stuff worth 8m gp?

Wands are great in use with shields. If you can afford go even for virtus one as better tier mean accuracy. I dont think polypore is now good if most spells cost nothing. For cheap magic you can use SoL along with ancient spellbook.

Don't use a shield.

 

I'm not sure if 2h or dw is better for magic when using abilities, but dw > 2h with momentum.

Yes.

Personally I prefer the Polypore because Wrack and Impact are much more powerful and accurate than with the wand.

 

For maximum efficiency however you will be looking to change spells according to weaknesses regardless of what weapon you use.

I don't think you can actually buy Ahrim's Wand & Book for the GE prices. They'll probably run you several million more.

I'd suggest picking up a Master Wand, which is currently less than 1m and only one tier below Ahrim's (tier 60 and 70, respectively), while also providing a Magic crit (no other Magic weapon does this as far as I know).

As for an off-hand, Grifolic Orbs are only tier 60 (same as Master Wand) but cost ~30k.

If fighting something using its correct weakness the loss of accuracy is negligible.

Master wand and literally any offhand will work. Even an imphide book is fine–the accuracy is almost meaningless on magic-weak enemies.