It can work either way. Usually, the child packages would be set to either inherit a variable from the parent, or they'd all be set to pick up the value from the same config file, but it's equally possible to have them inherit nothing at all.

So, I'd tread cautiously and check what the design pattern is first. Look at a few child packages and check their package configuration settings. I might even hack the host file for the test environment where you're running the packages from to make sure it can't even get to the prod environment in case you miss something!