2 different size torsion bars? what is preload?

Might be a silly question, but would there be ill effects of running 2 different size torsion bars? and 2nd is can someone explain pre loading? im getting nervous now that mine are in.... i saw it can only go it one way and with the adjuster and paw ALL the way down...slide it in then put back together right? i noticed when trying to get it in only one postion was close to match and fall in then add the pressure...did i miss something? what is this 30 degree etc?