Well I think professionnals will normalize to something between - 3db to 0db. I don’t really like that because then I always set the volume settings to like 10%.
I think my personal is to aim for - 3db but then I programmatically set the master to 50% volume by default.
And usually you keep like 6db difference between important audio and background stuff (voice lines and music for instance).
You could try the Godot Mixing Desk plug-in, I haven’t yet but I’ve heard it’s good.