I am not sure how well that works, as NVIDIA drivers need a karg and a blocklist of nouveau.
ffmpeg needs to be installed mit --allowerasing
While yes for sure flathub apps have support, you still have a preinstalled Firefox and a flatpak remote that both dont have the nonfree stuff. This is just very confusing.
But btw Firefox RPM has support for user namespace sandboxes, allowing process isolation. So just using the official Flatpak is not a real solution.