balena typically deploys your multi-container application to all devices in your fleet. There is no way to control the limit or increase the number of replicas, except for adding or removing devices. This model is tailored for IoT, since IoT customers typically deploy a device in many locations running the same application. Think of a device like a router. A router company might sell many routers, but they will all be running the same firmware.
There is also no in-built service mesh, device to device communication is less common. Using the router example again, router typically don’t talk to each other. They are typically controlled by connecting back to a central server in the cloud. There are of course mesh routers, in that case the users application must contain the logic for discovering other devices it is not provided by balena.
It is possible to deploy Kubernetes to all your devices using balena if Kubernetes features are required. This can be a useful way to manage a multiple cloud, on-prem or single board device cluster.