An RBA can be any metal/coil type you choose to build with, but you have to build it. Factory coils, the ones all made with cotton and all designed to screw in and vape are all Kanthal in the Beast line.
Preheat in TC (or wattage if the mod offers it) simply heats your coil to the set temp then the "regular" wattage you set as your highest current takes over. This is primarily useful with high metal mass coils that take much longer to get to temp. I find it unnecessary with simple round coils.