Could there be a chance of adding a split screen section or would any, if any split screen runs, be counted under normal coop

I'd say it counts as normal coop. Some runs are already posted as that. We don't like splitting the leaderboards more than absolutely necessary. This is the current format we have it in atleast, i cannot say how it will be in the future.

if submitting a splitscreen run would we both have to submit differtent videos or would just the same one of the the split screened run do?

One video of a splitscreen run will do. We can see both views in the same vid.