I set gfx.webrender.all to true and now it shows:
Compositing WebRender
But the choppy video and frame dropping issue still persists.
ENGINE BUSY MI_SEMA MI_WAIT
Render/3D/0 16.49% |█████▊ | 0% 0%
Blitter/0 0.00% | | 0% 0%
Video/0 0.00% | | 0% 0%
VideoEnhance/0 0.00% | | 0% 0%
^C