All 4 characters have level 50 in every skill, the best shields and class mods available, level 6 in all elemental artifacts, and a selection of weapons (a lot of them are not legitimately obtained in game, for example Chimera machine guns and sub machine guns that can proc all 4 elements).
The storyline missions for playthrough 1 and playthrough 2 are complete. Not all sidequests are complete. The characters are saved in slots 2 through 5 so your character will not be overwritten (though i still suggest making a backup).
Just to reiterate, these characters are not legitimately levelled. They are completely hacked, although the saves all work perfectly. This save is intended so that people can try out maximum level characters with a selection of mods and weaponry to aid in choosing the correct class.