Well, we don't know how and to what extent J-20 was used in that exercise. For all we know, they were flying mundane escort missions for other assets. Also, that exercise took place in China, whereas sending J-10Cs into Russia could be troublesome from OPSEC point of view. IIRC, J-10C does share quite a bit of avionic and sensor technologies with the J-20, which is why I said the sensitivity could be more elevated in this case.
I can't say for sure whether J-16 has the best avionics/sensor package of any Chinese 4th-gen platforms. It's certainly a highly capable airframe due to its size and intended mission profiles.