I am not finding much info on the bunjin style.

Look under literati, which is the (Italo-)English equivalent.

Is it treated differently than other styles, like it's not a true bonsai?


Au contrere, it is a quintessential bonsai style.

Also, is there a different fertilizer to use since you want long and thin
instead of
short and fat?

No, you still want slow, steady, controlled growth, unless it is a prebonsai in
training.
And you still want to encourage small leaves & twiggy branches.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)