What games are these like? Never played them and trying to o determine if I'd like them.
They're JRPGs set in post apocalyptic worlds haven't played through SMTIV and Apocalypse but in Nocturne the concept is rather than have a set party who join you on your journey you instead recruit the same demons you fight whether in battle or through other means like fusions and such. The post apocalyptic world is a unique setting as rather than the usual story types here it's a case of the world being remade or in the case of some of the other games what direction the world goes in so as a result every character you see is part of an ideal for which your choices with them determines your chosen ideal is in the end game, your choices and ideals also determines what bosses and such you fight.
Outside of the main story as you progress through the game you get the usual new side quests and such but certain things change for example you can return to an area and find an powerful optional boss is there, all in all it's a very deep JRPG.