Note that the order goes Muspelheim, colony (Turoq), Asgard.
[] Wait until Turoq lands then launch major attack- Highest chance of killing Turoq, rapid defeat of Turoq's forces, moderate ground losses and major naval losses
The truekill Turoq option. Significant losses to us and the Eldar both, however.
[] Wait until Turoq lands then launch major ground attack and naval harassment- Still high chance of killing Turoq, defeat of Turoq's forces, moderate ground losses and moderate naval losses
Less chance of True Death for Turoq, but plays to Eldars strength, which is harassment. Fewer losses, especialy for them. This is important, as they can not replenish those nearly as easily as we do. Also, their forces spend their time going around killing bad things, while ours mostly train and garrison (bar Avernites ofc), which makes theirs far more valuable to the galaxy at large.
[] Split warhost to reinforce all battles- Chance of killing Turoq, chance of defeat of Turpoq's forces, major reinforcement for other theaters
If we get Turoqs True Name, all that's needed is to get Areatha on the same continent as him, and enough luck to avoid him suiciding. So we still should have a good chance. Might not actually defeat Turoqs forces, but he will be dead/Dead/running away, and that should be enough to win this.
[] Have warhost reinforce Muspelheim- Rapid victory in Muspelheim, light naval losses
The do not Kill Turoq option, maximum help. Go all in right from the beginning, and then move to the next battlefield. Overwhelmingly good for us militarily, but Turoq will know and run away, likely with his entire fleet.
Now, this might not help him much. He is broke, and if we do not sustain major fleet losses here, we will be strong enough to launch an expedition to burn him and his to ash soon.
So, I think that we should do either of these:
Keep the Eldar back until Turoq lands. Then either split them to Muspelheim and the colony world both, or Turoq first, then move to reinforce Muspelheim. Use harassment. Move to Asgard when the battle there begins. The "Wait until Turoq lands then launch major ground attack and naval harassment" option looks to be the best fit, if not perfect.
Or
[] Have warhost reinforce Muspelheim- Rapid victory in Muspelheim, light naval losses