in terms of supergfx no idea, but nomodesetnomodeset usually means that you dont load the drivers, in this case i would guess nvidia drivers but bazzite has its own initramfs handler which would undo nomodeset because you are on the nvidia image and expected to use the nvidia drivers there
I've come back to report that steam link on Bazzite X11 is extremely unstable, it does work but more often than not, it will crash and reboot Bazzite just like on Wayland, it will only be quite delayed.
I've therefore concluded that X11 is extremely unstable on the legion go, and although it has perfect scaling, it is too unstable and buggy to run.
I am therefore going back to Wayland until one day in the future where X11 may get more stable.