I wouldn’t read too much into claims of a “wholly” Chinese design “besting” what are essentially Russian designs.
I would not discount it either.
The Chinese are doing some amazing things, and their own J-15, J-11B, J-16, etc. are as good as, if not better than the corresponding Russian aircraft.
Where they lack is engine technology. So they are not wholly “indigenous” when having to use Russian engines.
They have decent engines, but they do not measure up in power, efficiency, or maintainability to the Russian designs (which is why they still use them), Pratt & Whitney, Rolls Royce, etc.
What it will come down to is training, experience, and the sensors, ECM, and weapons.
I believe the Chinese are beginning to match in pure sensors. I believe their training is also catching up.
But they do not have the overall experience, the ECM is not as well known but I would rate it lower than the western designs and what Japan has, and I would rate the western/Japanese weapons as better, particularly in BVR, and in off-bore IR missiles.
But not a huge advantage in those last areas, because the Chinese are making rapid advances. It is something we and others cannot ignore, and where we cannot afford to sit on our laurels. The Japnese aren't.
Having said all of that, in a head to head matchup I would still give the match to the F-2...but a J-10B flown by an experienced pilot would be a very serious challenege and something that would have to be very respected.
I am looking very forward to the first flight of the new Japanese