I'm unfamiliar with the Trimma... Maybe somebody else can speak
My first thought is it probably would not bother him (at least at first), since he is already established in the tank. I only had problems with new comers. My SLW and True Perc. were eating buddies and didn't bother each other, but they were added within a couple weeks of each other.
The YWG may be alright as well. If he can make it down to a cave and especially if he pairs up with the pistol. My main concern would be with adding open water swimmers after the SLW establishes his home!