How to set the audio on unity

Hi everyone!

I'm currently working on an art project that involves a one scene
VR game built on untity and I'm kind of stuck on something!

here is my set :

I have the oculus headset plugged to my laptop, with sensors and all
(pretty usual), but I also have a video projector (plugged in HDMI to my
laptop) that projects on a wall the output image I have on my screen (I
don't know how to say it more precisely in english).

So, double question :

1 - How can I set the audio so that it comes out from the headset but also from the laptotp so that I can plug a speaker in it?

2 - When I build and run the game, I don't have any output image of
the game on my laptop screen unless I or someone puts the headset on,
wich is fine by me, but the sound is playing constantly, even when
nobody wears the headset. Is there a way to set the audio so that it
starts simultaneously to the output image, only when someone puts the
headset on? Like some settings or a line of code?

If someone has an idea it would help a lot!!

Thanks and have a good day!

cheers from France