I mentioned both in different contexts.

I’ve flown with Air China between the U.K. and Japan several times.

I would like to fly with China Airlines and spend time in Taipan.

Air China (not the Taiwanese carrier) ranks on the higher side of what I’ve experienced in Economy.

Pre-pandemic the Economy seats were considerably wider than those on their European competitors, legroom is also better, you are actually fed on all the legs not just the long haul flights, FAs have always been kind and accommodating (a big deal when flying with an infant), have never been hungry on a long Air China flight as there is something adequate in the galley, never gone thirsty either. Both my daughter and I are satisfied with the entertainment options. No horror stories regarding the state of the bathrooms.
Yes, connection isn’t great, but I’ve had horrible transfers at other airports (esp CPH) so not a dealbreaker. I avoid short transfers so I don’t get stressed.

I must not have explained myself about how long journeys eliminate jet lag for us. Where the stopover happens doesn’t matter. It’s about how your body experiences the journey, whether you get out at Istanbul or Shanghai or Taipei doesn’t really make a difference, the key is not to rest during the break. Longer you convince your body you are travelling, so long as you are completely pooped and ready to collapse when it is bedtime in Japan, quicker you adjust to the new regime.

Going back Westwards is different, shorter the better. We had the chance to fly JL41, an overnight flight from HND to LHR, on our last trip. Loved it!
(For the LHR to HND flight which left in the morning we stayed awake the entire night before arriving at Heathrow, our “stopover” was effectively London itself)