   Slot 1 has all characters at level 99, with maximum gold, maximum item inventory, the best armor, the best weapons, maximum magic skill, and all weapon skills at level 8.  I believe the only things not maxed out are their weapon skill, and Dryad's Mana magic which won't be activated until you beat Thanatos.  (I can't seem to figure out how to get all their weapon skill to go up to 8:99.  And yes, I've tried all the tricks I've found on various web sites--none of them worked.  But as far as I know, whether you're at 8:00 or 8:99 doesn't have any effect on gameplay.)  Slots 2-4 are saved at various points leading up to slot 1 (right before the raising of the sunken continent, right before reaching the Mana Tree, and right before using the trick to get the Mana Sword).  All are saved at the Wind Palace (great place to raise the girl's magic skills, if you've got the patience).
   I beat the game a couple times some years ago on an actual SNES.  But both times, I ended up saving the game after completing the Mana Forest, without getting the Griffin Helm (urgh!).  So after discovering the wonderful world of emulation, I decided to fully max out all the characters' stats and stuff.  Being a bit lacking in extra free time, I decided to speed things up by starting with Squidge's ZST with the hero starting the game at level 99 with lotsa gold.  Also, after getting the characters weapon skill levels up to 7 or 8 and their magic up to 5 or 6 or 7, with everything else maxed out except for the Mana Sword, I discovered Che's Secret of Mana Save State editor, and used that to boost the characters' weapon and magic skills up to level 8.  'Course, it still took quite a while despite those two cheats.  Hopefully the availability of this SRM will help prevent other obsessive-types from taking so much time to perfect their SoM game. :)
But enough rambling, now go kick some Master Ninja ass.

-Winane