The bankDetails required for a Payee depend on the currency and the type of payment you want to make to the Payee.

CurrencyRequired FieldsSupported Payment Schemes
GBPbankDetails.accountNumber
bankDetails.routingCodeType (SORT_CODE)
bankDetails.routingCodeValue
UK Faster Payments - FPS
CHAPS - CHAPS
EURbankDetails.ibanSEPA Credit Transfer - SCT

When a Payee is created, the response contains a paymentSchemes param which tells you the Payment Schemes via which the created Payee can be sent a payment.

"paymentSchemes":[
      "FPS",
      "CHAPS"
   ]
"paymentSchemes":[
      "SCT"
   ]