People tend to keep things separate and run multiple servers because of paranoia like this. But does that help? If someone had access to one device on your network (say you installed an app on your phone and you are on wifi) then can they access your server? Technically yes, right? So should you have a separate network and internet connection for your server, and place it in a different house down the street just in case? It starts getting silly and you have to draw a line somewhere. Most people choose to separate by function for practical reasons, if that has a security benefit, then that's a bonus.

StartOS itself is like a network with multiple machines. Each service you install is containerized and connected within the OS with a virtualized local area network. Services can access each other, but they can only access what has been exposed by the other service.