Another thing is that depending on the circumstance of Sui survival,you might still see large aristocratic clans monopolizing government offices.Yang Guang was vital for introducing the Imperial examination,which partially broke the aristocratic monopoly of government offices.
Basically Yang Guang as a ruler was both brilliant/incompetent/horrible at the same time.
As mentioned,he introduced the Imperial examination system.
Along with other measures like moving the capital from Chang’an to Luoyang and employing aristocrats from other regions of the empire,he tried to crackdown on the power of the powerful Guangzong nobility.This ended up alienating the Guangzong nobility—who then sponsored his cousin Li Yuan’s (the first Tang Emperor)revolt.
He built the Grand Canal,which would be vital for the economy of China as well as logistics for military campaigns,but because of the way how he built the canal in less than ten years with corvee labour,he created tremendous civil unrest.
His campaigns against Goguryeo most likely succeeded in heavily weakening Goguryeo,but all of his campaigns ended in defeat despite the massive advantage of Sui in numbers and equipment because of his inept military leadership(he basically tried to micromanage the war and did not allow hus commanders to take individual initiative).To fill up his army after repeated defeats,he had to conscript large numbers of men,which further destabilized his rule.
The guy also conquered other places like Tuyuhun and Champa,but most of his conquests were short-lived since the massive civil unrest meant that the areas he conquered had to be abandoned or re-conquered by his enemies.
Among other things,he was ridiculously greedy.Even though the granaries were overflowing with food,he still taxed his people heavily and refused to distribute grain to his people when his constructions or military campaigns caused famine.
If he died within the first ten years of his reign,Sui most likely would have survived while still having many of his innovations in place.