I work in Beijing and Tianjin. I would suggest that you either take a direct flight in, or transit outside China. The flight delays in China are very unpredictable so don't spoil your holidays over a missed flight.
Scoot flies direct to Tianjin, but sometimes it can be exp so check out Xiamen air which stopover (not transit) in Xiamen for just 1hr.
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Transit is less than 24 hours. Stopover is more than 24 hours.