A colleague who once worked for a not-to-be-named intelligence agency commented to me that Chinese avionics and human factors considerations in their Flanker reworks are a full generation ahead of their Russian counterparts. The J-11 and J-16 have cockpits stuffed full of MFDs and their avionics are - reportedly - mostly derived from Western civil systems from the late 1990s/early 2000s. They also have some structural differences - more composites and some internal structure changes - which cut several hundred kgs in weight from the airframes.
The big unknown for me are the engines (Shenyang WS-10). China has struggled for a long time with issues around thrust, reliability and operating life. The WS-10 is based off the core architecture of the CFM56, a 1980s civil airliner engine which is about as reliable as they come, and some other technology borrowed from the AL-31.
The WS-10 has been in development for better than 30 years at this point. The initial versions were reputed to have TBOs as low as 30 to 40 hours (mostly because of problems with erosion/disintegration of fan blades and production quality issues), engine lives under 200 hours and demanded as many as 15 man hours of maintenance for every hour of flight.
China reportedly 'borrowed' fan blade technology from Rolls-Royce in the mid 2010s, which has solved some of the problems. But, even the more mature WS-10B and WS-10C are reported to be maintenance hogs. Last I read, the WS-10B was roughly at AL-31FM reliability levels - i.e. about the same as an engine developed in the Soviet Union in the 1970s and reworked in Russia during the 1990s. Ballpark figures of life before rebuild of anywhere between 250 to 400 hours and full engine life of 1000 to 2000 hours.