As an alternative to #20 @herbdool suggests using hooks instead of CiviCRM Entity (pasted from Gitter below):
What's your use case for civicrm_entity? I've found it an unwieldy beast so haven't used it
I've usually just put a contact reference field on a node. If it needs to be automated then I've used hooks to call civi API. E.g create a contact when adding a node
[When a contact is merged or deleted in CiviCRM] gets more complex. It is similar problem to contact/user syncing.
this hook might help https://docs.civicrm.org/dev/en/latest/hooks/hook_civicrm_merge/
As for deleting contacts you might need to check on this hook if there's a node related to a contact https://docs.civicrm.org/dev/en/latest/hooks/hook_civicrm_postProcess. I'm not sure if it's called when a contact is deleted (it won't help with direct API deletion
This module will help figure out what gets fired when https://github.com/eileenmcnaughton/civicrm_developer
As an alternative to #20 @herbdool suggests using hooks instead of CiviCRM Entity (pasted from Gitter below):