With Hasura, it's easy to start with entity-centric GraphQL and add "custom" business logic mutations as required. Or you can use REST just for the latter too, nothing wrong with that.
Another question came my way, this time about entity-centric REST.
In short, don't do it.
Clients will have to do crappy round trips for joins. GraphQL helps with that.
But when it comes to multi-entity updates/inserts? You don't have transactions. That's going to be trouble.