In After the End, Brazil represents what China was to medieval western Eurasia: a large, centralized state that, should be slow to act, hard to expand, and tricky to maintain, but also not become mere "China-LARPing".
In order to achieve all of this, the mod developers are not only adding a few bonuses and restrictions, instead, a whole new set of mechanics, such as governments, contracts, succession laws, and realm laws, has been devised in order to allow the Empire, its vassals, and neighbors to steer the Brazilian Empire towards progress, stability, or pure ruin.
The main characteristic that is common to Brazil, medieval China and imperial governments as a whole is the bureaucracy. Even if peasants are the vast majority of the population and local lands are ruled in traditional, quasi-feudal ways, actual power resides in the hands of a vast, complex group of officials, civil servants, and courtiers that could set the whole country running in the right direction, or, more often than not, simply stall it. This is reminiscent of all great empires, such as the Ottomans, who are prime examples of this.
To do this, Brazil will not be a feudal monarchy, but an Imperial Bureaucracy. With the lawmaking power resting in the hands of the Emperor, and appointed officials, such as Governors or Captains, taking hold of the reins in the field.
One of the ways these vassals can influence the government, however, is by helping to pick the next emperor. Just like the Byzantine Empire, the hereditary rule is more of a suggestion, and inept successors will only be allowed if they have a strong enough backer. This is all mimicked by the Imperial Succession law.
Imperial Bureaucracies won’t have Crown Authority, but rather Court Authority, which can represent more power to Bureaucrats, to the Military, or, in rare moments of balance, to the Emperor. The Emperor, with his vassals, can negotiate special contracts that vastly change how the vassals will work. By assigning them to these, the vassal’s government form, and, perhaps, succession and realm laws too, will be changed, which come with many bonuses, penalties, and limitations.
All of these changes can be used to the Empire's benefit, and ruin. Compiling power in the hands of the emperor, ensuring his line is stable, or giving it to the vassals, who will make most of the lands under their authority, but also divide its political aims, is what will make or break Brazil. The developers of the mod are waiting on the next Crusader Kings 3 patch to go live, before enacting further changes, as they are closely tied to what the patch itself will change.