I need to specified the users that belong in an actor during the execution of the case, I don't know who is going to be able to see this until the previous human task finishes and indicates the id of the next users, it is required that these users can only see this task and no other
In order to have dynamic resolution to user in charge of the next task according to current case context, you have to use actor filter.
All required information is available on this Documentation page about actor filter