I have yet to see anyone create a thread saying something like 'I successfully connected my GPU RGB to my RGB controller/motherboard, everything is in sync, and this is how I have done it'. You see threads like that from time to time about custom fan, heatsink, and pump modifications. Instead, the only threads I have seen on this subject have gone something like 'I tried to connect my GPU to my system's RGB controller, and now my GPU LEDs don't work. Now what? Is my warranty now void?'. So, given the lack of success of those before you, I would not advise it. But, hey, if you get it to work by some stroke of genius, please post a guide so others can consider if they want to attempt to do the same.
Regarding the correct pinout, how to do it, voltages, currents, etcetera, you are on your own in uncharted territory.