For any% group do you all just start up the game at the same time? So when the first character gets control thats when you start the timer? I assume the whole group has to be starting a new character right?

Yeap whole group starts a new char. Timer starts when you get control of your character.

So everyone just has to join as soon as possible on one guy?

and do all parties need to be recording video?

Nope, however it would make quite a cool video haha