Are there any first come first served camping areas?

Yes there is

Yes. But many local people go and “reserve” them them by going and paying for a site and putting a card on it a few days before they can physically be there. It’s best to talk to the camp host and see what’s not taken. We were there, just a few weeks ago, with a reservation made 90 days before, and most walk sites were “reserved” in this way. I wouldn’t trust that I could just happen on a good site on a Thursday or Friday by walk up. Hope that helps.