Re: WS-10 vs. WS-15 TVC.
It seems unlikely that a WS-10 TVC variant would be fitted to operational J-20s given the associated weight and performance penalties. It could still be useful for testing purposes in terms of refining control laws, however.
The first half of this video is great, with shots that last seconds -- entire seconds! -- before it descends into modern rapid cut rubbish. Digital editing has a lot to answer for.
Fun fact: it was so cold during the filming of the opening shots that the photographer got sick and barfed on the floor.