A lot of banks simply use the SPs/HPs performed when application of credit is performed as enough. There are a few banks however like US Bank that use other services like Innovis and SageStream to supplement their information to verify employment, income and so on. Additional services like Lexis Nexis and the work number are a few others off the top of my head that a few lenders use to verify information as well. Plus, any additional data can be gleaned if you past/current relationships with them like deposit history
As for verification if a bank has issues confirming your identity they will contact you and have you perform security checks such as text confirmation, sending copies of driver's license, and so on. Varies by bank really in the end. I wouldn't worry too much about it but be ready just in case
