Monzo will be consulting the community about their plans for these 
They haven’t announced the TransferWise integration yet..
My assumption is that just like declined Direct Debits, there won’t be a fee for these.
Presumably they’ll let us know about any other charges once they’ve been decided.
If you’re not comfortable about ‘missing information’ I’d recommend not signing up for a current account until you have it. There’s no pressure on you to sign up right now.