When campaign completes successfully, you will have to capture all transactions for that campaign. If it is not successfully completed, you will have to void the transactions.
All payments go in project owner Stripe account. The fees go in your Stripe account.
You should communicate by email or phone with your users to get information about their bank accounts or other options to send them the money.
There is no options for requestion a withdrawal. However, it is good idea and I can implement it in next release. I have some ideas to improve the payout process and communication between project owner, administrator and users in next release. I hope to be able to publish next release at the end of next month. If you have any ideas and suggestions, I will be very grateful if you share them with me. I can implement time.