When adding a custom customer attribute or custom customer address attribute, to allow Magento to save it you need to assign it to the customer attribute set.
So, in your code, after $customerSetup-&...
To identify this issue you can follow below steps :
Disable any third-party extensions and check if the slow account creation issue persists.
If the problem is sorted out re-enable the extensions one ...
You can send notification with the use of observer. You need to have email template id , sender information and receiver information.
Please follow below steps.
Step 1: Please create ...