As of yesterday YB is low, cold, and very clear. There are some midges when it's sunny and I even saw a few BWOs but surface activity was virtually non-existent and I had to fish very hard with nymphs to get a single fish.
Susky has more water in it but big WW rivers cane be very tough this time of year IMO, especially for FFers. I'd try to find some slow, deeper eddies and fish a big streamer right on the bottom very slowly. You might get a bass or three or maybe a walleye. Fallfish are active this time of year and are often found schooled up in the same summer spots long after bass have departed. They fight like a wet rag in cold water but can save a day if nothing else is biting.
Sunny days with a warming trend are your friend if you plan to hit rivers.