Hi welcome aboard
I'm a Real Fleet Boat fan (RFB) just love the way its orgainised and the sinking machanics the modders have incorperated into the game.
Couple this with Run silent run deep and it is so imersive!
The New Trigger maru is quite something, beta 1.8 version brings a whole host of new features to the game.
Havent really tried Fall of the Rising sun or Operation Monsoon iI'm afraid.
But I would suggest it's wothwhile playing stock a bit to get a feel for the game before lauching into the modded game personally.
Whichever way you go happy hunting