You can use any wire you want, heck I have seen people use solid wire even, but the wire that is sold for RC is probably the best stuff out there for our application, and this is from a licsensed electrical contractor. Also unless you have a really high amp draw application 14 gauge wire is probably plenty big for anything we do, pulling a continuous 30 plus amps might need bigger but there are not going to be many cars that pull that continuously, seeing as your highest amp draw is during accelaration. As for fiber optice, thay dont pass electricity at all they pass laser light, not much good for electric motors and due to bend radius rules would not even be any good for connecting controller parts together.