It could be anywhere from 1000 CFS down to 500 CFS.
Browns is runnable down to 317 CFS (my lowest run).
August is great in Brown's because the weather is so good and the water nice and temperate. To me it's still the most scenic run on the Ark (and maybe that's not saying much, but still). You'll have a good time at any of those flows.
Watch out for rafters. The window to put on is either before 9 a.m. or between about 11 and 12. You miss the boat launches at those times.
If flow is below 800, I recommend putting in at Ruby Mountain rather than Fisherman's Bridge to avoid slow flatwater between the two.
"self-aggrandizing jackass" - it says it right on the label