There are no score extends in Guwange. My guess is that it was the '1-up' item you get for killing the stage 4 midboss without bombing. There are a few 1-up/health refills scattered all around the game, like the one in stage 3 that you get for destroying the big statue with the shikigami.
Really, if you just play for survival, Guwange is pretty easy. You have almost as much wiggle room for getting hit as in a lot of Touhou games, and the bombs are really high-damage. But playing like that isn't very fulfilling really. Guwange is a scoring game first and foremost. If you really want to play it, you gotta play for the chain. :V
And for 1cc vs. 1-All, I believe the first refers to non-looping games while the second is to looping games. For instance, if you 1cc DDP's first loop, you got a 1-ALL, while 2 loops would be 2-ALL. Then for non-looping games like Touhou, it's just '1cc.'
edit: HOLY SHIIIIIIIIT 33 COIN CHAIN IN GUNBIRD 2
FUCK YES YOU ARE THE BEST SCORING SYSTEM EVER
edit2: i r gud spellr