The South Fork of the Salmon will likely be at flows above six feet which makes the SFS Class 5 / 5+ kayaker-only whitewater.
If you are looking for a mellower trip look for flows below 5 feet. River flows can change in a hurry that time of year as well.
I'm hoping that sounds exciting to you, because it's one of the best / biggest / scariest whitewater runs in the world.
At mellower flows it's still challenging but you can enjoy the scenery, spend more time enjoying everything, and not get flushed into rapids you should scout.