I can't speak for Kotor 1 and 2 since I've never played them, but as is usual with BioWare games, conversations between characters have multiple choices with game-changing outcomes. The story of course is rich and deep, and much darker than previous BioWare games. The fighting is basically you running up to an enemy and hitting the attack button...but your character won't stop attacking until they or the enemy are dead, or you issue another command. You can control anyone in your party individually, and the game is not over if your main character dies (as you can continue as another party member until you defeat the enemies, in which all characters come back to life). I believe there's 6 races of characters, and multiple jobs for each one. Also, there's a ton of different endings.