200e

I believe you are correct in that the 261e uses an analog circuit to achieve wave shaping, & I believe the other points to be a question of the sample rate & bit resolution of the circuits and software behind the 200e.
I think it bears repeating, I love both the 261e and 259e.

Not that it is a purely digital limit, rather a digital circuit with multiple 
analog 1/0 demands, which would lead me to think in terms of separate rates for audio versus control where they see fit. It would not surprise me to however find the external audio fm input to be governed differently than the internal (presumed software hardwired) fm connection between a mod osc to carrier, though I don't hear a difference.
Also, to make things more interesting is noticing how a 291e patched to self oscillate responds to audio fm through it's audio fm inputs.