If the Actor or Stuntman were right in the middle of the fire in Forever is doubtful. In movies its just about illusion, Its pretty clear in a few of the shots, Specially when its Kilmer who is around the fire. The fire is either a few metres away from him, on the front,back and sides. Mostly Visible when he get "out" of the fire and looking at Two-Face. (I can be wrong, Its been a while since i saw it).
But, When the fire is coming right against Batman, Im pretty sure it was a stuntman. The cape effect was probably a mix of actual liveshots and CGI to make it look extra glossy and give the "shield effect". The cape was never explained, But it was clearly a fireproof cloak activated by the button inside his belt as shown in the movie.
Back on the fire scene in Begins. If you look closley in Begins, You can see the Gel that is covered on the silicone suit and the stuntmans face, In the apartment and right after he lands on the street and stumbles away.
I think they did a better job with the fire scenes in Forever.