In Quick submit, after you have made all of your talent selections for each role, you can review this by clicking on the orange number on the left hand side.
If you'd like to remove any talent that you may have added, simply click on the X on that talent, and that will remove them, and you can review them here.
You can choose to submit each role to casting one at a time using this button here, or you can click on the submit all selected to casting, which will submit your selected talent on all of these roles. You can customize from the selected page rather than customizing each time as you select a person. It may be easier to do all of your customizations after you've selected all of the talent you'd like to submit, like switching out primary images or updating any submission notes that you might need.