Hello Damian and Thank you for your answers !
Let's start for last point : I already made two virtualhosts but for a typo It did not work but now it's fixed ! For the other two points I was expecting a reply for jitsi developers since much of options to tweak cam and audio is not documentated.
Regards - John
Regarding your first question, from my experience, I received some
recommendations to put in config.js [resolution: '720',] to fix the camera
resolution, but it didn't work. Jitmeet stills make the automatic balance
without taking into account that variable.
Regarding your second question, I'm sorry I don't have the answer.
Regarding the third topic, following the guideline
https://github.com/jitsi/jitsi-meet/blob/master/INSTALL.md you will be
able to have both working in the same server.
Hope it helps.