yeah 1200 and stanza arms are the same lenght, but the main difference is the different bolt spacing for the balljoint
dont know about the castor arms thing though, as im using modded 1200 castor arms with my sunny/stanza lcas

120y stub axle angle is different to stanza, but it should actually give more neg and allow less wheel clearance

the track increase (without measuring) would come from the ball joint being longer/further out and the hub and what not also being bigger/further out

but i use TRX rims so have no trouble with excessive track width