The consequences for the decision with Delane are clear cut, want a strong orc army? give her to the orcs (Ulcro or Baltri to favor Andras, Tarish to favor Jezera). Want a diminished orc army? help her escape
Now if you let her escape, Tarish will be hostile towards Rowan and if you don't have a strong army to put her in her place or can roll enough Diplomacy she will continue acting this way. You won't see Delane again until you reach Rastadel. And then if Rowan picks Jacques or Crevette as an ally, you will only get a few interactions, a couple of lewd scenes, and Rowan convincing her to escape before the sack of the city. But if Rowan goes for Werden, then she will have a pivotal role to get him as an ally, nonetheless this means that Mariane gets to escape and Delane is the one who will meet the fate the twins had prepared for her