I'd say people go 1/2" because they plan on expanding their system at some point. If you plan to use a march pump they require 1/2" on the inlet side, and you restrict flow on the outlet. It's a one time purchase, and worth a few extra bucks to do it 1/2" the first time around.
For cleaning, Bar Keepers Friend and/or Oxyclean work great and are at your local supermarket. BKF is good for scrubbing crud away and leaving a nice finish, Oxy is good for dissolving the crud, use it with hot water and let it soak.