I have a medium sized Revelate Tangle bag on a 56cm CrossCheck and 56cm 26" wheel LHT that doesn't impede pedaling. I carry a heavy 4' chain in it on one side that takes up half the space. Light thin clothes can fit in there but not all the items you mention. Maybe light rain pants and jacket, or shorts, windbreaker and socks with snack bars and small camera or phone lined up in the narrow left pocket.