I'm not familiar with the Nightcutter, but if it's like other implementations of 1W Luxeons and optics, the Fraen gives that smallish but pretty even square spot. An NX05 optic (a direct swap) would give a small squarish center hotspot with little star pattern around it, and a medium large modest side spill surrounding. An IMS So17xa reflector usually fits fine, although the legs may have to be trimmed. It gives me a small round center hotspot and modest, large sidespill.
I think changing the glass lens affects the amount of transmission but not the beam pattern.