Hopefully this is true, can you please confirm that you can adjust the other states now?
Yes that is correct, i am not using power tables for doing overclocking+undervolting when using OverdriveNtool 0.2.6. I didn't like WattMan and poewrtables are a pain in the butt for finding the "right" one for each card so I tried and found out that it's possible only with overdriventool <3 . GPU-Z shows power consumption 115w per card, it's not real from the outlet, but pretty close because of power supply inefficiency so it's working for undervolting and overclocking is working as well.
I am using a profile with the low states disabled by clicking on letter P0, P1, etc. I don't use those states but you may try if It works to have low states working. This is my config for vega56, don't know if it's the best, but works for me.
http://oi68.tinypic.com/2s7x9qo.jpg