As i said, all audio is played, including FiveM main menu background music, which has nothing to do with servers. In fact, the main menu background music (which plays through FiveM GTA process itself, not the chromium browser sub process) does not play if you have “Music Volume” set to zero, so it should not play on focus loss either. The same rule should apply to audio streams that do play via chromium process, though.
I’m not sure what you mean by “global” but you definitely can control the volume of FiveM audio streams globally. They play through “FiveM Chromium subprocess”, which has it’s own volume control on windows mixer.
Anyway, i am aware streams audio streams can be tied to the “music volume” setting via server script. Not sure servers can tell whether “mute of focus loss” is enable or not, though. I’m reporting because i believe this should be a client game setting, not dependent on servers to fix it.