I have a fairly aggressive tank with a cowrie and 1 mexican turbo snail. Now the cowrie doesn't do too much--he's a bit lazy! He does though only move at night. Once the lights go off he starts cruising. I'm sure that is due to his tankmates!
The mexican on the other hand does move freely about the tank even during the day. My triggers either haven't noticed him, or are not interested in having him for lunch.
I have never had a trochus snail, but have heard good things about them as far as putting them in aggressive tanks. Good luck!