I can tell you for a fact that the stock wire on the 50V was stranded copper - near zero ohms. When I found the bike, it had a generic NGK style 5K resistor cap on it.
Somewhere I have an OEM cap, but not sure if it's good. I'll try to check it out at some point soon. So far, the 50V runs perfectly with the 5K cap.
Water cooling on the Solo is passive.. I've been wondering myself just how much it does, but my guess is that the main benfit is evening out the heat in the cylinder. I'd like to know what Solo said about it.