Re: Connecting two high gain fully differential opamps &
offset cancellation
it's necessary for high-gain amplification, otherwise you may have to increase the size of your input diff. pair to make a ultra-low-offset input.
anyway, it finally depends on how large the gain is. If the gain is not so large and you can tolerate some drift of the DC point, you'll be fine.
btw, even though you've solved the offset problem, noise and distortion would be another issue for high-gain amplification.