FCFS with NO reservations available, however there are plenty of sites available both in the upper section by the highway and down by the lake. We stayed in June 2022 and there were only a handful of us.
FCFS when we were there, but this was almost 2 years ago exactly, so this may have changed. Not sure when you’re planning on going but I think of the 20 or so spots there, 4 were taken including us. And as I said that was this time of year.