Ok now it’s clear and it seems perfectly doable. I’d expect the server part to be able to handle a 6v6 FPS on a single Google VM.
As regards the two builds, I am not sure how much stuff can be stripped off of the two executables. In theory they need most of the assets in order to either apply the server logic or just render them on client. Maybe you could use conditional compilation to exclude code that is not needed on one side? I am not sure, though.
Yeah, as you said it’s deprecated, so it would probably be best to look into a possible replacement:
https://discussions.unity.com/t/727663