I prefer to use a messenger bag for commuting, shopping and riding around the city, once in a while I'll use my roll top backpack both are 100% waterproof (sealline brand). I've tried a rack with a bag on top of it and I also have panniers but I just don't like to use them for everyday riding because the bike feels awkward and heavy. I like to keep my bike flickable and light ,it's easier to manuever and bunnyhop. . I often ride some unpaved narrow singletrack trails on my way home so panniers wouldn't work for me. The only time I would consider using panniers and rack is if I was touring for a couple of days.