I think disabling networking “until I’m ready” would conceptually be a failure of free software. Rather than containing systems inside of on-off switches, it is better if the systems are under my control and do what I desire.
But, to your second point, I ought to look more at startup settings. That sounds like a good idea. I’m on i3 at the moment so I don’t know if it has the same kind of setting(s) in the same kind of places, but maybe I will find them.