On Silverblue, there is a difference between the rpm-ostree version of Firefox that installs by default, and the flatpak version. The flatpak offers better codec support. Is the same true with Clear Linux? Would I get better multimedia support if I installed the flatpak and deleted the default bundle?
Firefox from bundle doesn’t support multimedia playback by default. This is a guide on how to fix it: How-to: h264 etc. Support for Firefox (including ffmpeg install).
I think you will get better performance out of the bundle one, since it’s optimized for Clear Linux.
Flatpak is a generic version if I understand correctly and doesn’t have CL’s optimizations, but yes, it will work out-of-the-box, Firefox bundle will need some tweaking for videos.