The project is here, first release is out:

https://github.com/halsafar/Vega64SoftPowerTableEditor

Basic overview of the power table:

http://www.overclock.net/t/1633446/preliminary-view-of-amd-vega-bios

Hellm post about modifying the power table for Vega:

http://www.overclock.net/t/1633446/preliminary-view-of-amd-vega-bios/250#post_26297003

More details to come about how to setup xmr-stak-amd with a Vega 64 to achieve 1900H for 150W at the wall.