Your issue is one of either preference or necessity. There is no easy way to estimate your needs because only you have total grasp of the issue. As far as preferences, I would use separate repos for the application and worker code and deploy them with Envoyer. I don't feel that Envoyer is the correct tool for the DB server and the load balancer is just config. The only reason to use Envoyer with Forge is to not have interruption in service/access. Envoyer allows for many processes to run during deployment like stopping workers and restarting or route caching whatever.
Additionally, I would like to mention that many people confuse Envoyer the service with Envoy. Envoy is a task templating system that works great with server deployment tasks.
For more information on Envoy, go to https://serversforhackers.com