BLDC Control using Inductive Resolver

Hi All,  New here, so please correct any etiquette mistakes!  

So we want to use an inductive IPS2200 based encoder/resolver for a BLDC/PMSM design.

Plan is for driver to use Trinamic TMC4671 with absolute encoder for rotor position.

Not quire sure of the nuance differences between absolute encoder and resolver but marketing materials says it works great!

So thinking to pick resolver from the 80 reference designs.  Could use some help picking the best one and understanding how optimal it is vs. other options. 

I do have a specific question about the resolver vs. absolute encoder.  Why/How does the number of motor poles matter.  My tiny brain thinks - don't you just need to know the position of the rotor as precisely and accurately as you can - regardless of number of poles?

So our basics are a 100mm outrunner frameless motor with 36 poles.  The shaft we are spinning is 1.5" or 38.1mm diameter. 

Will a Renesas Resolver 4.0 work for us? Or why can't I just convert the sin/cos output to an absolute encoder signal and number of poles doesn't matter?  Or am I missing something?

Any help choosing or rejecting this approach appreciated - free or paid.  

Thanks for reading!