Historical Progression of San Chin
We do not know what the original Higaonna open-hand san chin kata looked like, but based on description it seems Uechi-esque (As an aside, Tou’on-ryu has never and does not teach an open hand version of the form). We know that Kyoda taught his version of San Chin fairly close to what Higaonna settled on (i.e. it was Higaonna who closed the hands and not Miyagi Chojun). And we know again through oral tradition that Miyagi modified the breathing of Higaonna's san chin and introduced his own version. Therefore, for me, the structural and historical progression (using Uechi as a substitute) would be the Uechi-Tou’on-Goju.
We do not know what the original Higaonna open-hand san chin kata looked like, but based on description it seems Uechi-esque (As an aside, Tou’on-ryu has never and does not teach an open hand version of the form). We know that Kyoda taught his version of San Chin fairly close to what Higaonna settled on (i.e. it was Higaonna who closed the hands and not Miyagi Chojun). And we know again through oral tradition that Miyagi modified the breathing of Higaonna's san chin and introduced his own version. Therefore, for me, the structural and historical progression (using Uechi as a substitute) would be the Uechi-Tou’on-Goju.