Alucard is as he appears through the second castle of Castlevania: Symphony of the Night. He is equipped with masamune katana, holy sword, goddess shield, beryl circlet, mojo mail, crystal cloak, lapis lazuli, bottle of holy water, faerie familiar. He has the Mist relic with the Mist time extension and poison.
Sora is as he appears in Kingdom Hearts 2 FM+ with his best non-broken equipment, and is able to use his Valor, Wisdom, Limit, and Master forms, though they aren't infinite, use the same gauge (starting with and limited to 5), and won't eat up an ally. He doesn't have Magnet, summons, limits (except in Limit form), any reaction commands, or invincibility.
Zack is as he appears in Final Fantasy 7: Crisis Core. He has the Buster Sword and is bringing along offensive, command, independent materia. All his limits are maxed, and the only limits he has access to are Chain Slash, Octaslash, Rush Assault, Meteor Shots, Lucky Stars, and Apocalypse.
Cloud is as he appears in FF7 and the KH games. He can glide freely and has limited flight. Cloud has access to all his limit breaks, the three main elements, Comet 1&2, Flare, Ultima, the Cure spells, Bio, Berserk, Esuna, and various buffs and debuffs.