in general, it is not good practice to change the notifications settings, as it will have a negative effect later on. You can, during drafting up the project, use 'dummy' placeholder resources which will not take up 'real' resources (and you can set them up with dummy email addresses). Once you are ready to assign real resources, you can do that and they will receive notifications as needed. A more advanced way is to build a customization that will not send email notifications while not in Active state (for instance). I would recommend touching base with your customer success manager if you are interested in that option.