It's quickly becoming obvious the J-20 is going to be focused on interception and interdiction along the lines of the old MiG-25 with an added strike functionality, and the aircraft relying most probably on speed and stealth to allow it to challenge enemy aircraft and surface vessels without getting detected, launch a volley of AAMs or ASMs, then run away.
Despite claims from chinese defense sites, the traditional Delta-Canard layout of the the wings and surfaces indicate similar functionality to the Dassault line of fighters which are meant to be missile launchers, and are "less maneuverable" compared to more contemporary designs. The addition of the tailplanes partially solves this, but as proven by Delta-Canard contemporaries like the Mirage, Rafale, Gripen, this config is prone to energy loss in dogfights and are thus not meant to engage in long-duration furballs.
Chengdu's reluctance to do a full airshow routine is probably to hide the poor energy management of the platform, as well as the underperforming local engines... though if they go full production with the Saturn AL-31s, they might have better kinematic performance.