Eldorath and Kith both have "after" effects when they commit to a planet. If they commit to the same planet can Eldorath use his ability to exhaust the Khymera token that Kith creates?

If Kith player has initiative does her ability trigger first and in this case make the answer to above question yes?

The player with the initiative would decide who triggers first.

The player with the initiative would decide who triggers first.

The way this is worded might be a little misleading.

If multiple triggering conditions are created at the same time, the players may play reactions to any and all of them during their reaction opportunity. The player with initiative does not get to decide "who" triggers first; the player with initiative gets the first opportunity to use a reaction. But their choice of which triggering condition they react to does not force the other players to play reactions to that triggering condition before moving on to another one.

So, for example, say that the Eldar player has initiative. He gets first reaction and uses Eldorath's reaction to exhaust a unit. Immediately after that, the DE player would have the opportunity to trigger Kith's reaction; they don't have to wait until the opportunity to play all other reactions to committing Eldorath (e.g., Foresight) have been played or passed on first.

Similarly, if the Eldar player has initiative, if he tries to say "you react first" to the DE player, that would be considered a pass on reactions for ALL available triggering conditions. If the DE player the decided NOT to trigger Kith, that would be consecutive passes and the Eldar player will have lost his opportunity to use Eldorath's ability.