ok so I am considering buying a frame and building it up into my dream bike. As I have never done this I am confused about the bottom brackets. I understand that italian and british bottom brackets are basically just different threadings. However, when you buy a frame does the bottom bracket come prethreaded or would you need to have it threaded? Also are carbon fiber frames any different than metal frames? (i.e you have to get an aluminium frame drilled, but carbon fiber is pre drilled because of technical reasons?) thanks.