If my Iphone 7 plus has IOS 13.1.3, can I use phone to phone migration on a new Iphone 11 with IOS 13.0?

After you've activated your new phone, then yes put it near each other, you will see a prompt saying it needs to upgrade your 11 to 13.1.3 after that is done, then the data is transferred.

Yes, it will update your iphone 11 to the new version and then do the transfer.