Bandwidth optimization for few short conferences

We have a jitsi (latest stable) deployed server (16 GB RAM, 8 core) with enough bandwidth.
here is our config :

https://testcon.kloudtalk.com/config.js

we, at client side lets say has a Bandwidth limitation of 2Mbit/s up speed and 2Mbit/s down speed. client want to prefer laptop audio (without headset or headphone). is it ok to have a good conference with 15-20 people with this environment with video on?

testing result was horrible - audio breaks, lags and even sometimes vanishes (tried to tune the configs but no major improvement) and video quality is not problem for now (as we just wanna have good fluent conference first so I reduced the bitrate and resolution) but it lags and vanishes by it’s own wishes. client side bandwidth touch bottleneck even with 3-4 persons.
Can you suggest why this is happening and what I should do or where I have to look into? I noticed that even after enabling simulcast every one’s up speed is near 1Mb/s all time (shouldn’t it be highest only when he is on focus after enabling layer off-stage-layer-suppression?) and others’s down speed also seems high alltime max possible and jump to so much high with every person enters the conference. where (video-bridge ?) can I see those bandwidth limitation/control logic and tweak myself while up from client and route from video bridge?
Thanks in advance :heart:
@damencho @xranby after long time…!

Do you have this enabled jitsi-meet/config.js at bca9a12df1b5effbc48904303567670552b8bd29 · jitsi/jitsi-meet · GitHub

yeah. I have simulcast and suppression layer enable