This is and interesting question. I don't think Larian will answer it so as not to spoil things but they did say that there will be a price to pay for embracing it the same as with the tadpole...there is the allure of great power for doing so but you might end up alone. So I suspect that the more you give in to the dark urge the more you lose control, but that's just a suspicion. Still if you plan to just fully resist it all the way and never give in then I don't think it will override any choice. Also of note as demonstrated in the gameplay showcase, the dark urge choices aren't always what they seem, like when Larian chose to "imagine" ripping that guy's hand off and then the player character really did it...a slippery slope for sure and could definitely derail some of your intended plans to go through the game.
