Synthetic Backups

We curently have arounf 50tb of files on our file server, split over various jobs that are Full to tape and Incrementals to disk (and duplicated to tape).

I want to move to disk based for all the fulls (synthetic) with duplication to tape.

1. Would the synthetic full from disk to tape be any quicker than going directly to tape?

2. Would the synthetic full from tape to tape be any quicker than going directly to tape?

3. Could incrementals run whilst the synthetic full was being run or would it be superseded - (I want to increase the frequency of incrementals)

thanks!