So with my coins stuck in Yobit with pending withdrawal, if they somehow return my coins will I still be able to use them since they won't be on bittrex during the swap?
Yes, the swap will have a certain time duration. So if the swap period has started already you can still send your coins over to Bittrex as long as it is within the swap period. This period is still being determined and will be announced, but will likely be several weeks (possibly longer).