Help using Mangohud / Gamemode with Flatpak version of Lutris and Steam

Like the title says I am trying to understand how these things should work together. Part of my issue is I don't have a good mental model on the Flatpak permissioning / sandbox model. My use case is running a game on Lutris, which is a Flatpack, and using my package install of Mangohud. I am also curious if I should using a...