RE: Wide or narrow tires for truggy?
think you want thin for loose and wider for hard tight surfaces. The thinner the tyre, the more pressure it will put down on its narrower surface area. Wider tyres have less pressure due to their wider contact area with the ground. Narrower tyres in most cases will bite better, wider will have a tenancy to slide a little more.
Correct me if I'm wrong, I don't race, I'm just using my poor knowledge of physics!