Could it be divided into Type A, B and C?

Type A pb 14:48 Type B pb 14:41 Type C pb 15:25

What exactly is the difference between A B and C? Just fire pattern/rate?

I guess if I'm not sure

The fire pattern and rate, yes, which affects speed of killing bosses, particularly in the original version of the game as bombs deal 1/3 as much damage as Batsugun Special Version. Currently, Type-B makes the other ships essentially pointless because it's so much better than both of them.