There are several strategies that can be adopted to get better performance, stability, and scalability out of Jitsi Meet. By taking certain precautions, we can increase the number of participants in a room, as well as the quality of the call.

1- Use Chrome/Chromium: At the moment, the browser that best supports the use of Jitsi is Chrome. During a conference, the resoulción of the videos that each participant sends changes, adapting to the number of participants. The quality decreases as others join, so the load on bandwidth and CPU is minimized. FireFox is not able to receive this information and adapt the resolution of the video it sends, so each connection made with this browser ends up overloading the whole call. Firefox is working to resolve this situation, but in the meantime, avoid using this browser to join the rooms.

2- Don't use the Mobile App: With the Mobile App the result is the same as with FireFox. One solution is to use the Chrome browser in 'Desktop view mode' mode and access the room through its public link, as you would do from a computer.

3- Audio Input: check that your audio is not generating echo. A single person generating echo will end up disturbing the whole room. Set the audio input on your device to an optimal level to send the signal without amplification.

4- Use headphones: This minimizes the possibility of echo being generated in the room

5- Mute the microphone: if you are not speaking, keep your microphone off. This reduces noise and increases the overall quality of the call by reducing the amount of data sent. For a satisfactory dynamic of your meetings you can use the request to speak functionality.

6- Disable the camera: Whenever screen sharing or viewing of participants' videos is not required, you have the option of disabling the video. This will allow you to create rooms with many more guests.

Here you can check latest published functionality of the tool that can be useful for you:

https://jitsi.org/news/features-update-april-2020/