First of all welcome to our world 😎
You should use the core hooks and only in cases that they do not fulfill your needs to deploy custom ones.
In this scenario, actionCustomerAccountAdd is just fine I guess. View more
PS. When you deploy custom hooks you need 3 steps:
- You register the hook (a record is created in the respective table if does not exist already)
- You define the module action for the specific hook
- YOU CALL THE HOOK (either in custom file or in override of any kind) like here
It is natural that nothing happens because there is no hook call 