I’m glad that I finally see someone testing Jami by streaming video games.
I had some similar issues - maybe you can try out and post issues on Gitlab.
Now regarding your questions/ comments:
Specifically it looks like Jami was optimizing for maximum FPS
If you are using the integrated option of Jami to share your screen (NO virtual cam or hdmi capture card):
In the past:
screen sharing is at 30 fps for all platforms.
See: Question: frame rate of the screen share (#1262) · Issues · savoirfairelinux / jami-project · GitLab
However, it will now be possible to select the fps: Desktop sharing frame rate (#514) · Issues · savoirfairelinux / jami-client-qt · GitLab
I had similar issues (test call same account, different networks: Windows 10 → Android) especially if I was using OBS-VirtualCam.
Maybe you can try out if you have the same or similar issues so the developers can fix these issues:
The rest of your question I can’t answer.