Glad you figured it out! A separate network for a set of services that need to talk to eachother is the way I do it for my selfhosted tools, if you want some more ideas on setting up the *arr apps using docker compose, this is my current setup: https://github.com/hosaka/selfhosted/blob/main/servarr.yml
I think it’s is not aimed to protect against potential attacks, this is aimed at a developer using/writing modules of code. This is not a security guard