After Effects Can you help me find out if my idea will even work using Ater Effects and CA

[Craig Hilton]

Please help, can you use the lip sync feature during a head turn? Will all mouth animations follow the movement of the head, including size and angle changes? i am planning on using after effects on my real life stop motion clips (silicon models). So basically similar to robot chicken, but instead of using stickers for mouth movements i would use after effects. In theory it seems like a possibility, but no-one seems to have attempted this. can i have a video clip in the background and animate over it (video is a previously recorded animation.) 2D animation over a 3D animation. Thank you (first YouTube comment = be nice)