Employee Expenses

We are thinking of switching our accounting system to QuickBooks on-line and trying to decide whether we go with Plus or Advanced. One feature, Employee Expenses might make us go with Advanced but the info on how the employee expense feature works is pretty sparse. Currently, we use Certify. We have about 10 expense submitter employees. I’m wondering if QuickBooks can replace Certify altogether and streamline our expense management processes. I have some questions:

1) Do expense submitters count as users? What happens if you surpass 25 users?
2) What do the submitter employees use to record expenses? Is this the QuickBooks app, an expense app or a mobile web site?
3) Can expense submitters use the app/website to record mileage? Can we determine the mileage rate?
4) How are expenses actually submitted? One by one or do submitters prepare a monthly expense report (i.e. with individual expeses in that report)? Each or of our submitters might have 30-50 (sometimes more) expense line items. Are all these individually submitted one by one?
5) To whom are expenses submitted? Can we set up a specific person who will only have access to that approval feature?
6) Can expenses be rejected? Can the approver request additional information from the submitter before approving?
7) How are expenses reimbursed? Currently this is done in Certify using and ACH payment where we pay the entire expense report.