Bazzite lead developer here, we actually never used the flatpak. Our first release had it installed in a distrobox container on the desktop images. Deck images always had RPM Steam because Steam is essentially functioning as a desktop environment there. We moved them both to be RPM for support consistency reasons.
Only the kernel module is open source, and it’s just a wrapper for closed source blobs.
In actuality the open source drivers just kill all support for the 10 series, and otherwise do nothing to fix Nvidia’s utterly fucked up driver problems.