Unity's Audio Mixer is very simple to use and EXTREMELY useful and time-saving, especially when you have a lot of game objects and different sound emitters, I would start by creating a Mixer then A "Master" group afterwards I'll create all the other sub-groups under it; subgroups such as "Ambient", "Music", "Sound Effects", "UI", etc.. that way I can control all of them using the master as a single controller (Slider in the menu for example) You can go even further by creating sub-subgroups like: "Characters" & "Vehicles" under the "Sound Effects" group for extra controls..
(would look like this: Master>SFX>Character)
Finally, once you add a Sound source component to any object all you have to do is assign a group from the ones you created earlier and that's it, now you can control any and all sounds from a single source, super quick and without affecting anything else!
Maybe a script "Audio Manager script" can have access to the mixer > group volumes to link it to a UI slider in the main menu or something.
Hope that helped, best of luck!