Ok , so I got chance to have a play around tonight . It seems that the slow video playback is only on the first watch , and then after that it plays back fine. Although the frame dropping and simplifying subdivisions of the character helped a lot too.
As for the grease pencil, it is still behaving strangely. Ive managed to get it so that it draws a seperate image on each frame, and only shows the image drawn on that particular frame, but the issue now is that whatever the FIRST drawing I make is, stays on every frame. So if I draw a GP line on frame 1 , thaht one stays throughout the whole animation whilst others drawn after that only show on the frame they were drawn on. It means that the first pose I draw over Wayne in the ref, stays there right through, but the other poses disappear like they should when I scrub through. BUT this happens nomatter what frame I make my FIRST GP line on , so If I open up the file and jump straight to frame 30 , and make a GP line, and then scrub back to frame 1 , it is still there, and is there on EVERY frame.
EDIT** I think ive figured out the GP, the first stroke was going on layer 1, and the second on a new layer, so the first was hanging around even when you drew another stroke because the new strokes were going on layer 2.
