We will use the male Light Infantry`s as examples of generation.
Soldier: Only Romancing SaGa 2 characters has this rank.
Low Level James to Herbert.They can grow 20 times.3 LP.
They aren't special, nor any good, they only shine when you are learning about the game. They are more of a nuisance, because if you want an General or High Soldier, good luck with an 83.4% chance of Soldiers popping out.
High Soldier: This is the lower level of most King and the event characters. Ronald and Harry.They can grow 25 times.4 LP.These ones are very interesting to use, since some are better than General characters, with their only bad point their HP, they sure can pack a punch when raised correctly.
General: The lower level of Emperor characters, and the alternate weapon choice of them.Axe user James.They can grow 30 times.5 LP. They aregreat replacement for Emperors, as they have great stats(Victor, Harid and Lute, for example) and nice versatility.Great characters overall.
Event: The middle level of Emperor characters, most of them use another weapon type that their General and Emperor counterparts don't use.The Seven Heroes cannot be Emperors.They can grow 30 times.5 LP. Meh, just an same stats as Generals.
King: The superior level of Divine Soldiers, they are no main characters, which makes them inferior to Emperor characters. Dwight and Franklin.They can grow 35 times.6 LP.
Emperor: They are the superior counterparts of General and Event characters, these are main characters or legends, also the superior level of the first generation of Romancing SaGa 2, like James, Lisa, Hector, etc and the level of the Altamenos line(Adel, Ivan, Lazareth, Finnith, Olga and Iris).They can grow 40 times.7 LP.The ultimate class, shame that EVERY character is becoming Emperor. Well, they are ultimate above all others, they boast high attack, defense and agility, but, if you cannot have one, the Generals are there to fill that gap.