20AWG: normally used between the battery and the power distributor (busbar), or for instruments with high power consumpion (radio, bugwipers, ...). Maximum current 11A.
22AWG: normally used between the power distributor (busbar) and the instrument, or as signal wire. Maximum current 7A.
TEFZEL is an Aviation Grade wire type that is easy to solder and strip (much better than Teflon!), and is very flexible.