Twintex is described by the manufacturer as being repairable, It can be welded but it is very difficult to get anything to stick to it as it is a polypropylene based material.

I don't know the details of this boat, but from the renderings it definatly looks to have some kind of surface finnish. I think that gelgoating a Twintex boat defeats the object somewhat as the Gel coat would fracture in an impact.

A plain Twintex finish is available in black or off white. A black finish looks like this