Well, this is the time period of Byzantium I'm least familiar with: Was the Union a whole-sale adoption of Latin rite, including the Latin Mass, or was it a symbolic union?.
Actually this "union" was in fact a submission of the orthodox church to the Papacy... Orthodox Bishops and Lords were required to aknowledge the Pope as their superior...
Orthodox view considers Pope as another Patriarch "Primus inter pares"
while Catholic view considers Pope as a universal Bishop whose authority is above other Patriarchs and Councils...
The desperate Emperor was forced to accept the Papal Primacy in a last effort to save the ruined empire...