How confident can you be that a match on a PEP is real and not a fake positive?

Very confident!

As the PEP list used in BankID AML has close to 100% coverage with date of birth (or SSN for Swedish PEP's) you can be fairly certain of a real match if you include the persons date of birth in the search. Additional information in the service, such as address etc. will help determine cases of doubt.