From what I understand flatpak contains all the binaries and libraries required to run the contained program. So the packaged games come with a version of wine and DLLs that are known to work. You are basically copying a known good installation from somebody else.
PlayOnLinux and Lutris use all your native binaries and run scripts that are supposed to make the game work.
This approach can still cause trouble e.g. when using a newer/older version of wine than the script’s author used.
This is such a good idea.
EDIT: I stand corrected. PoL and Lutris actually manage wine versions. They still use native libraries though while flatpak will use the exact executables known to work. Thanks @mihawk90
@StrY please report back whether you got fortnite to work. It’s supposed to be broken ever since they activated anti cheat. Epic has switched from BattlEye to “simple anti cheat” though, so maybe that one works?
I can’t even get the launcher to run on my system