I daresay realism.
I think you are underestimating the court forces at play, the obvious divergence I had assumed you were going for was the 100 Days Reform not being only 100 days and continuing. I think the problem is that in 1829, China isn't that far behind the west and still believes in splendid isolation. I think it would take some stimulus to prompt Qing westernisation, such as Britain or France or Portugal or whoever deciding to try to take some land, maybe the Netherlands try to reclaim Formosa to repay the previous expulsion? This sting of defeat would make the court realise that the Sinosphere is no longer as strong in relation to others as it once was.
In this context, Tibet, Mongolia and Korea who all remained tributaries until the end would likely be peacefully annexed, unless their rulers fought back in which case order is restored to the rebellious provinces and they join the Empire.
Japan was too far gone from the Sinosphere geopolitically to just be invaded, and they would likely have a stronger navy due to earlier Westernisation. The best a Qing state could hope for is cultural subservience and close alliance as Japan was no longer just a series of worthless islands.
A stronger Qing state would also have needed to prevent the Taiping rebellion being as bad as it was historically for them to resist Han claims that the Manchu's were no longer fit for purpose.
Agree mostly. Would only hazard the statement that the Taiping rebellion in this timeline may not even have taken place, at the least not in the explicitly anti-Manchu way that it did - the social dislocations of the First Opium War and the ensuing opium epidemics especially in the south-east are missing, which - assuming no coincidentally similar breakdown of administration - already drastically reduces the relative appeal of the various bandit groups to the local populace vis-a-vis the state authority. Crucially matters though what exactly changes: Is the examination system adapted to allow for the growing class of would-be elites to join officialdom, or are they still frustrated by the notoriously hard exams? Would a strong Qing state allow for the proselytising of British and other missionaries inside its borders? What about the extraterritoriality of the Treaty of Nanjing and what that implies for the power of the Qing state versus the foreigners to protect the locals - since, in our timeline, Christian converts were increasingly protected by their churches and even ambassadors to the point where the local Qing officials learned not to try and bother about their transgressions? Would western modes of thought and ideology still hold the same power that they did IRL if the traditional Qing court cosmology, rhetorical though as it may have been meant to be, did not appear to break down as the foreigners began to dominate the Qing, again especially in the southeast - the later heartland of the Taiping, if the apparent link between the Confucianism of the emperor and the natural harmony of the Chinese state did not break? Would late-Qing Han racial nationalism still emerge among the student and intellectual classes if the relative power of the Manchu-ruled Qing state was maintained - indeed, why should it if the western belief systems were shown to be inferior to the culturalism of the Qing intellectuals by virtue of the successful defense of the Qing state against the foreigners (again, emphasising the maintenance of traditional cosmology)? What happens to Japan as one of the key tributary states - if the traditional order is not inverted through successful Meiji and unsuccessful Tongzhi/etc. reforms, what happens instead? Going beyond the 60s - what happens to the historical attempts to reform - Tongzhi, Guofan, Hongzhang, Youwei, Qichao, Guangxu? What has so drastically shifted the balance of power at the court in favour of the reformers long before any apparent need for change was there? What form does the impetus to reform takes is imho also crucially important - does it come from the west or is it somehow internally generated? Even ignoring the impact of the west for a moment, though, which imho to some degree merely revealed how kaputt the state really was - what happens to the disconnection between local and central government, to the inefficient and outdated taxation system that far too heavily relied on overtaxed peasantry and unregulated and unpaid tax agents? What happens to the military structure of the state - does the decentralisation and personalisation of army generalship resulting from the Taiping, Nian, Dungan, and Panthay rebellions, as well as from the various Opium Wars, still take place - presumably not, but if not, what else leads to military reform?
As plenty of others have said - far too many butterflies.