Is it best (for security) to install browsers via Flatpak or via a distribution's repositories on Linux?

Well, Mullvad doesn’t even list Flatpak on their installation page (Mullvad Browser for Linux) and the Flatpak on Flathub (https://flathub.org/en/apps/net.mullvad.MullvadBrowser) isn’t official, so it is likely safe to say they recommend installing it as an RPM. I do wonder, however, if I should layer it? Because layering packages with “rpm-ostree” is considered by some “a last resort” (Package Layering - Bazzite Documentation) and have “MAJOR caveats” ( Package Layering - Bazzite Documentation ). This is just from the Bazzite documentation, but it is still fairly trustworthy I think.