What did you find out about the differences between R2.0 and R3.0?
From the ASRock website it looks like they have different hardware layouts and the OEM BIOS packages are different. The specs are similar but slightly different. That's all I know.
Link to R2.0: https://www.asrock.com/mb/Intel/H110M-DVS%20R2.0/ Link to R3.0: https://www.asrock.com/mb/Intel/H110M-DVS%20R3.0/
Best regards, Alex