996 definitely doesn't apply to Korea. Korea's Labor Standards Act amended in 2018 allows for a maximum of 52 hours of work per week, down from 68 hours before. They're quite strict on it to the chagrin of many in the tech/IT/media industry, making it much harder for them to meet deadlines on projects and such, there's plenty of news covering the complaints of game developers, TV production sets and so on and so forth about the difficulties posed by the labor law.
As for contractors, Korean contractors are among the fastest in the world so that part is irrelevant vs Taiwan or China. When Taipei 101 was under construction, the TFCC, which owns the building, transferred the entire construction authority over to Samsung C&T Corporation to expedite the build out. Earlier this year, Samsung C&T was selected to build a new terminal at the Taoyuan International Airport, so no, the Koreans do not have a disadvantage in that regards.
On the other hand, labor cost in Korea is definitely higher than Taiwan. Minimum wage is substantially higher in Korea (roughly $9.25/hr) vs Taiwan (roughly $5.25/hr). In fact, minimum wage in Korea is higher than Japan (roughly $7.50/hr) and the United States ($7.25/hr). Just three days ago, there was a report released showing Korean college graduates starting salary at companies with 500 employees or more is 59% higher than the equivalent salaries at conglomerates in Japan.
Taxes are generally higher in Korea vs Taiwan and R&D deductions are lower in Korea vs Taiwan, military spending as percentage of GDP much higher in Korea vs Taiwan, and another factor to consider is, Korea's always had cheap electricity due to favorable policies towards nuclear energy, that all went to the crapper with Fukushima and President Moon's administration, causing huge losses for KEPCO and raising electricity bills across the board. Taiwan will face energy issues too with their decision to follow suit with phasing out nuclear energy, both countries have very limited land for solar and to meet renewable energy targets, have to spend heavily on offshore wind which is $$$.
But as someone else pointed out above, Korea has a wide variety of industries that are competitive on the world stage. Car manufacturing, ship building and locomotives, household appliances, media and pop culture, batteries, petrochemicals, food and pharmaceuticals, Korea has a strong presence in all these industries, whereas Taiwan, outside of TSMC and semiconductors, you have a few EMS supplying IT equipment with relatively low margins, Formosa Plastics in chemicals (also affiliated with Nanya), some banks/financial institutions, and Evergreen? In that sense, I fear Taiwan has too many eggs in one basket with TSMC. As much as I dislike TSMC having a near monopoly on leading edge processes and not having a viable competitive second source, maybe the fact they're dominant in semis will be a good enough reason for the rest of the world to rally behind them to stand up to China, which to me is more important in the big picture of things.