opamp input bias voltage vs. common mode rejection ratio
Consider a typical example of an op-amp having 1 mV offset voltage and 100 dB CMR. 

CMRR is \$\dfrac{differential\space gain}{common\space mode\space gain}\$

So, if the differential gain is 1000 and the CMR is 100dB (100,000), then the common mode gain is 1000/100,000 = 0.01

It can be seen that differential offsets are by far more liable to produce an output error compared to common mode voltages. For this reason it is sensible to assume that the offset voltage of an op-amp has no contribution from the common mode voltage.

Regards input offsets being affected by frequency, remember that all op-amp offsets are a dc quantity. I'm not saying that high frequency EMI doesn't tweak these offsets a little - there are a lot of examples where EMI can produce a pseudo DC offset at the input due to input protection rectifying the high frequencies to a small DC value.